AppHelper not found

Following migration to 2.3, after 'cake database' and 'cake setup', attempting to view the app via browser fails with a blank page and these errors:

[30-Jan-2013 16:46:23] PHP Fatal error: Class 'AppHelper' not found in /Applications/MAMP/htdocs/r406/trunk/lib/Cake/View/Helper/HtmlHelper.php on line 31
[30-Jan-2013 16:46:23] PHP Fatal error: Class 'AppHelper' not found in /Applications/MAMP/htdocs/r406/trunk/lib/Cake/View/Helper/FormHelper.php on line 28

2013-01-30 16:46:23 Warning: Warning (2): include(/Applications/MAMP/htdocs/r406/trunk/lib/Cake/View/Helper/AppHelper.php) [<a href='function.include'>function.include</a>]: failed to open stream: No such file or directory in [/Applications/MAMP/htdocs/r406/trunk/lib/Cake/Core/App.php, line 540]
Trace:
App::load() - CORE/Cake/Core/App.php, line 540
App::load() - CORE/Cake/Core/App.php, line 540
spl_autoload_call - [internal], line ??
include - CORE/Cake/View/Helper/HtmlHelper.php, line 31
App::load() - CORE/Cake/Core/App.php, line 540
spl_autoload_call - [internal], line ??
class_exists - [internal], line ??
HelperCollection::load() - CORE/Cake/View/HelperCollection.php, line 129
View::loadHelpers() - CORE/Cake/View/View.php, line 884
View::render() - CORE/Cake/View/View.php, line 463
Controller::render() - CORE/Cake/Controller/Controller.php, line 947
PagesController::display() - APP/Controller/PagesController.php, line 80
ReflectionMethod::invokeArgs() - [internal], line ??
Controller::invokeAction() - CORE/Cake/Controller/Controller.php, line 485
Dispatcher::_invoke() - CORE/Cake/Routing/Dispatcher.php, line 186
Dispatcher::dispatch() - CORE/Cake/Routing/Dispatcher.php, line 161
[main] - APP/webroot/index.php, line 96

2013-01-30 16:46:23 Warning: Warning (2): include() [<a href='http://php.net/function.include'>function.include</a>]: Failed opening '/Applications/MAMP/htdocs/r406/trunk/lib/Cake/View/Helper/AppHelper.php' for inclusion (include_path='/Applications/MAMP/htdocs/r406/trunk/lib:.:/Applications/MAMP/bin/php/php5.3.6/lib/php') in [/Applications/MAMP/htdocs/r406/trunk/lib/Cake/Core/App.php, line 540]
Trace:
App::load() - CORE/Cake/Core/App.php, line 540
App::load() - CORE/Cake/Core/App.php, line 540
spl_autoload_call - [internal], line ??
include - CORE/Cake/View/Helper/HtmlHelper.php, line 31
App::load() - CORE/Cake/Core/App.php, line 540
spl_autoload_call - [internal], line ??
class_exists - [internal], line ??
HelperCollection::load() - CORE/Cake/View/HelperCollection.php, line 129
View::loadHelpers() - CORE/Cake/View/View.php, line 884
View::render() - CORE/Cake/View/View.php, line 463
Controller::render() - CORE/Cake/Controller/Controller.php, line 947
PagesController::display() - APP/Controller/PagesController.php, line 80
ReflectionMethod::invokeArgs() - [internal], line ??
Controller::invokeAction() - CORE/Cake/Controller/Controller.php, line 485
Dispatcher::_invoke() - CORE/Cake/Routing/Dispatcher.php, line 186
Dispatcher::dispatch() - CORE/Cake/Routing/Dispatcher.php, line 161
[main] - APP/webroot/index.php, line 96

2013-01-30 16:46:23 Error: Fatal Error (1): Class 'AppHelper' not found in [/Applications/MAMP/htdocs/r406/trunk/lib/Cake/View/Helper/HtmlHelper.php, line 31]
2013-01-30 16:46:23 Error: [InternalErrorException] Internal Server Error
Request URL: /registry/
Stack Trace:
#0 /Applications/MAMP/htdocs/r406/trunk/lib/Cake/Error/ErrorHandler.php(183): ErrorHandler::handleFatalError(1, 'Class 'AppHelpe...', '/Applications/M...', 31)
#1 [internal function]: ErrorHandler::handleError(1, 'Class 'AppHelpe...', '/Applications/M...', 31, Array)
#2 /Applications/MAMP/htdocs/r406/trunk/lib/Cake/Core/App.php(926): call_user_func('ErrorHandler::h...', 1, 'Class 'AppHelpe...', '/Applications/M...', 31, Array)
#3 /Applications/MAMP/htdocs/r406/trunk/lib/Cake/Core/App.php(899): App::_checkFatalError()
#4 [internal function]: App::shutdown()
#5

2013-01-30 16:46:23 Warning: Warning (2): include(/Applications/MAMP/htdocs/r406/trunk/lib/Cake/View/Helper/AppHelper.php) [<a href='http://php.net/function.include'>function.include</a>]: failed to open stream: No such file or directory in [/Applications/MAMP/htdocs/r406/trunk/lib/Cake/Core/App.php, line 540]
Trace:
App::load() - CORE/Cake/Core/App.php, line 540
App::load() - CORE/Cake/Core/App.php, line 540
spl_autoload_call - [internal], line ??
include - CORE/Cake/View/Helper/FormHelper.php, line 28
App::load() - CORE/Cake/Core/App.php, line 540
spl_autoload_call - [internal], line ??
class_exists - [internal], line ??
HelperCollection::load() - CORE/Cake/View/HelperCollection.php, line 129
View::loadHelpers() - CORE/Cake/View/View.php, line 884
View::render() - CORE/Cake/View/View.php, line 463
ExceptionRenderer::_outputMessageSafe() - CORE/Cake/Error/ExceptionRenderer.php, line 303
ExceptionRenderer::_outputMessage() - CORE/Cake/Error/ExceptionRenderer.php, line 284
ExceptionRenderer::error500() - CORE/Cake/Error/ExceptionRenderer.php, line 242
ExceptionRenderer::render() - CORE/Cake/Error/ExceptionRenderer.php, line 175
ErrorHandler::handleException() - CORE/Cake/Error/ErrorHandler.php, line 122
call_user_func - [internal], line ??
ErrorHandler::handleFatalError() - CORE/Cake/Error/ErrorHandler.php, line 235
ErrorHandler::handleError() - CORE/Cake/Error/ErrorHandler.php, line 183
call_user_func - [internal], line ??
App::_checkFatalError() - CORE/Cake/Core/App.php, line 926
App::shutdown() - CORE/Cake/Core/App.php, line 899
[main] - [internal], line ??

2013-01-30 16:46:23 Warning: Warning (2): include() [<a href='http://php.net/function.include'>function.include</a>]: Failed opening '/Applications/MAMP/htdocs/r406/trunk/lib/Cake/View/Helper/AppHelper.php' for inclusion (include_path='/Applications/MAMP/htdocs/r406/trunk/lib:.:/Applications/MAMP/bin/php/php5.3.6/lib/php') in [/Applications/MAMP/htdocs/r406/trunk/lib/Cake/Core/App.php, line 540]
Trace:
App::load() - CORE/Cake/Core/App.php, line 540
App::load() - CORE/Cake/Core/App.php, line 540
spl_autoload_call - [internal], line ??
include - CORE/Cake/View/Helper/FormHelper.php, line 28
App::load() - CORE/Cake/Core/App.php, line 540
spl_autoload_call - [internal], line ??
class_exists - [internal], line ??
HelperCollection::load() - CORE/Cake/View/HelperCollection.php, line 129
View::loadHelpers() - CORE/Cake/View/View.php, line 884
View::render() - CORE/Cake/View/View.php, line 463
ExceptionRenderer::_outputMessageSafe() - CORE/Cake/Error/ExceptionRenderer.php, line 303
ExceptionRenderer::_outputMessage() - CORE/Cake/Error/ExceptionRenderer.php, line 284
ExceptionRenderer::error500() - CORE/Cake/Error/ExceptionRenderer.php, line 242
ExceptionRenderer::render() - CORE/Cake/Error/ExceptionRenderer.php, line 175
ErrorHandler::handleException() - CORE/Cake/Error/ErrorHandler.php, line 122
call_user_func - [internal], line ??
ErrorHandler::handleFatalError() - CORE/Cake/Error/ErrorHandler.php, line 235
ErrorHandler::handleError() - CORE/Cake/Error/ErrorHandler.php, line 183
call_user_func - [internal], line ??
App::_checkFatalError() - CORE/Cake/Core/App.php, line 926
App::shutdown() - CORE/Cake/Core/App.php, line 899
[main] - [internal], line ??