For anyone that might still be stumbling over this, there appear to be two issues in the source. The first major one is the use of the reserved word 'debugger' ~line 314 in ajform.js:
debugger : _debugger
You should be able to either delete this line or rename it, i.e.,
debugit : _debugger
Second issue is near the top of the same file. IE doesn't always like a trailing comma, so...
2009-02-11 21:30:55 UTC in AJFORM - AJAX Javascript Toolkit
