upgraded to 7.09 and now join button has stopped working

i upgraded from 7.5 all the way to 7.09 doing each upgrade one at a time and now join button isnt working, any ideas?...i dont want to start a new install .

http:thegroupconnection.com

regards

Dean

that happens in ie9, when try in firefox i get this -

Warning: Due to a documentation error in previous version of HTML Purifier, your definitions are not being cached. If this is OK, you can remove the %HTML.DefinitionRev and %HTML.DefinitionID declaration. Otherwise, modify your code to use maybeGetRawDefinition, and test if the returned value is null before making any edits (if it is null, that means that a cached version is available, and no raw operations are necessary). See Customize for more details invoked on line 588 in file /home/****/public_html/inc/utils.inc.php in /home/******/public_html/plugins/htmlpurifier/HTMLPurifier.standalone.php on line 2031

Warning: Cannot modify header information - headers already sent by (output started at /home/****/public_html/plugins/htmlpurifier/HTMLPurifier.standalone.php:2031) in /home/******/public_html/inc/design.inc.php on line 133

anyone?

http://www.boonex.com/forums/topic/error-comes-up-on-join.htm