MediaWiki internal error.

Original exception: exception 'AFPUserVisibleException' with message 'Error in regular expression "" at character : "Undefined index: flag"' in /usr/local/apache/common-local/php-1.5/extensions/AbuseFilter/AbuseFilter.parser.php:1604
Stack trace:
#0 /usr/local/apache/common-local/php-1.5/extensions/AbuseFilter/Views/AbuseFilterViewEdit.php(419): AbuseFilterParser::regexErrorHandler(8, 'Undefined index...', '/usr/local/apac...', 419, Array)
#1 /usr/local/apache/common-local/php-1.5/extensions/AbuseFilter/Views/AbuseFilterViewEdit.php(385): AbuseFilterViewEdit->buildConsequenceEditor(Object(stdClass), Array)
#2 /usr/local/apache/common-local/php-1.5/extensions/AbuseFilter/Views/AbuseFilterViewEdit.php(37): AbuseFilterViewEdit->buildFilterEditor('<p>There is a s...', 'new', NULL)
#3 /usr/local/apache/common-local/php-1.5/extensions/AbuseFilter/SpecialAbuseFilter.php(107): AbuseFilterViewEdit->show()
#4 /usr/local/apache/common-local/php-1.5/includes/SpecialPage.php(559): SpecialAbuseFilter->execute('new')
#5 /usr/local/apache/common-local/php-1.5/includes/Wiki.php(233): SpecialPage::executePath(Object(Title))
#6 /usr/local/apache/common-local/php-1.5/includes/Wiki.php(62): MediaWiki->initializeSpecialCases(Object(Title), Object(OutputPage), Object(WebRequest))
#7 /usr/local/apache/common-local/php-1.5/index.php(116): MediaWiki->initialize(Object(Title), NULL, Object(OutputPage), Object(User), Object(WebRequest))
#8 /usr/local/apache/common-local/live-1.5/index.php(3): require('/usr/local/apac...')
#9 {main}

Exception caught inside exception handler: exception 'AFPUserVisibleException' with message 'Error in regular expression "" at character : "Only variables should be passed by reference"' in /usr/local/apache/common-local/php-1.5/extensions/AbuseFilter/AbuseFilter.parser.php:1604
Stack trace:
#0 /usr/local/apache/common-local/php-1.5/includes/memcached-client.php(1075): AbuseFilterParser::regexErrorHandler(2048, 'Only variables ...', '/usr/local/apac...', 1075, Array)
#1 /usr/local/apache/common-local/php-1.5/includes/memcached-client.php(801): memcached->_flush_read_buffer(Resource id #89)
#2 /usr/local/apache/common-local/php-1.5/includes/memcached-client.php(413): memcached->get_sock('enwiki:gadgets-...')
#3 /usr/local/apache/common-local/php-1.5/extensions/Gadgets/Gadgets.php(79): memcached->get('enwiki:gadgets-...')
#4 /usr/local/apache/common-local/php-1.5/extensions/Gadgets/Gadgets.php(55): wfLoadGadgetsStructured()
#5 /usr/local/apache/common-local/php-1.5/extensions/Gadgets/Gadgets.php(171): wfLoadGadgets()
#6 [internal function]: wfGadgetsBeforePageDisplay(Object(OutputPage), Object(SkinMonoBook))
#7 /usr/local/apache/common-local/php-1.5/includes/Hooks.php(132): call_user_func_array('wfGadgetsBefore...', Array)
#8 /usr/local/apache/common-local/php-1.5/includes/OutputPage.php(1011): wfRunHooks('BeforePageDispl...', Array)
#9 /usr/local/apache/common-local/php-1.5/includes/Exception.php(159): OutputPage->output()
#10 /usr/local/apache/common-local/php-1.5/includes/Exception.php(186): MWException->reportHTML()
#11 /usr/local/apache/common-local/php-1.5/includes/Exception.php(284): MWException->report()
#12 /usr/local/apache/common-local/php-1.5/includes/Exception.php(343): wfReportException(Object(AFPUserVisibleException))
#13 [internal function]: wfExceptionHandler(Object(AFPUserVisibleException))
#14 {main}