These are some issues that we have run across in development and that have been reported to us. Some may or may not happen to you.
CFMX Specific
If you are running under shared SSL, with a URL such as http://secure.yourhost.com/yoursite/, the CFIDE will still be missing unless your host places it at the root of secure.yourhost.com. You may wish to ask your host about this issue. In some browsers there are no errors and in others there are. So just because you are not seeing errors does not mean no one else on your site is. In version 8.7.5 we deleted all the CFFORMs on the secure checkout pages and the cf_searchform custom tag (since that may be called from secure pages also).
CAUTION! If you are installing cf_ezcart on your own personal server, and installing it in the main web root of the server, where the actual CFIDE folder is installed, be certain NOT to upload this folder, lest you overwrite the actual CFIDE. This is why we named it CFIDE for CFMX, so you don't overwrite the original by accident under this scenario.
Other Versions
Note! In version 8.7.5 we have done away with all CFFORM tags. Preliminary testing on ColdFusion 5.0 seems to show that the this bug may have gone away with the CFFORM tags. We believe this was caused by all the excess code that CFFORM places within the <head></head> tags of the templates. You should test your application using cflocation first as that is the most desirable method of redirection.