Helllo! I purchased Forms Toolkit yesterday and am experiencing the same error as the original poster whenever attempting to add a ShowIF behavior. The message I get is "While executing applyServerBehaviour in WAFV_ShowIF.htm, a JavaScript error occurred."
I have attempted all the previous fixes mentioned previously, including deleting the AppData cache file, uninstalling and reinstalling the Forms Toolkit extension, etc. I have also checked and double-checked all Javascript code. Nothing works.
I have zipped one of the pages which is experiencing the issue. Thanks, in advance, for your assistance.
Jeremy