Firefox 18 contains a new JIT compiler which breaks the MooTools javascript used for the forms.  It is known to break checkbox and radio selects in AWBS.  It could also affect other areas of AWBS.  If you notice issues with your site since upgrading to Firefox 18 even with sections that do not include checkbox and/or radio selects it is highly recommended to download and apply the patch provided here.

Download patch for Firefox 18