MediaWiki internal error.

Original exception: exception 'MWException' with message 'Non-string key given' in /usr/local/apache/common-local/php-1.17/includes/MessageCache.php:508
Stack trace:
#0 /usr/local/apache/common-local/php-1.17/includes/GlobalFunctions.php(780): MessageCache->get(2011, true, false)
#1 /usr/local/apache/common-local/php-1.17/includes/GlobalFunctions.php(743): wfMsgGetKey(2011, true, false, true)
#2 /usr/local/apache/common-local/php-1.17/includes/GlobalFunctions.php(643): wfMsgReal(2011, Array, true)
#3 /usr/local/apache/common-local/php-1.17/skins/Vector.php(657): wfMsg(2011)
#4 /usr/local/apache/common-local/php-1.17/skins/Vector.php(539): VectorTemplate->renderPortals(Array)
#5 /usr/local/apache/common-local/php-1.17/includes/SkinTemplate.php(518): VectorTemplate->execute()
#6 /usr/local/apache/common-local/php-1.17/includes/OutputPage.php(1721): SkinTemplate->outputPage(Object(OutputPage))
#7 /usr/local/apache/common-local/php-1.17/includes/Wiki.php(372): OutputPage->output()
#8 /usr/local/apache/common-local/php-1.17/includes/Wiki.php(157): MediaWiki->finalCleanup(Object(OutputPage))
#9 /usr/local/apache/common-local/php-1.17/includes/Wiki.php(58): MediaWiki->preliminaryChecks(Object(Title), Object(OutputPage))
#10 /usr/local/apache/common-local/php-1.17/index.php(114): MediaWiki->performRequestForTitle(Object(Title), NULL, Object(OutputPage), Object(User), Object(WebRequest))
#11 /usr/local/apache/common-local/live-1.5/index.php(3): require('/usr/local/apac...')
#12 {main}

Exception caught inside exception handler: exception 'MWException' with message 'Non-string key given' in /usr/local/apache/common-local/php-1.17/includes/MessageCache.php:508
Stack trace:
#0 /usr/local/apache/common-local/php-1.17/includes/GlobalFunctions.php(780): MessageCache->get(2011, true, false)
#1 /usr/local/apache/common-local/php-1.17/includes/GlobalFunctions.php(743): wfMsgGetKey(2011, true, false, true)
#2 /usr/local/apache/common-local/php-1.17/includes/GlobalFunctions.php(643): wfMsgReal(2011, Array, true)
#3 /usr/local/apache/common-local/php-1.17/skins/Vector.php(657): wfMsg(2011)
#4 /usr/local/apache/common-local/php-1.17/skins/Vector.php(539): VectorTemplate->renderPortals(Array)
#5 /usr/local/apache/common-local/php-1.17/includes/SkinTemplate.php(518): VectorTemplate->execute()
#6 /usr/local/apache/common-local/php-1.17/includes/OutputPage.php(1721): SkinTemplate->outputPage(Object(OutputPage))
#7 /usr/local/apache/common-local/php-1.17/includes/Exception.php(189): OutputPage->output()
#8 /usr/local/apache/common-local/php-1.17/includes/Exception.php(220): MWException->reportHTML()
#9 /usr/local/apache/common-local/php-1.17/includes/Exception.php(325): MWException->report()
#10 /usr/local/apache/common-local/php-1.17/includes/Exception.php(393): wfReportException(Object(MWException))
#11 [internal function]: wfExceptionHandler(Object(MWException))
#12 {main}