CFWebstore locks all writes to application and session variables, as well as some large area of reads. If you are using CF version 4.5, you should have the Variable Scope Lock Settings in the Administrator all set to automatic read locking, or no automatic checking. I'm having trouble getting Authorize. Net to work. Double-check that your settings at Authorize.
Net are correct, and try turning off ALL required fields.
Jpegs saved from some graphics programs seem to confuse the imginfo custom tag. This tag should handle any jpeg or gif. When I do a search in my store, some of the links don't take you to the right product. If you delete or add products or categories, and are using the Verity search, be sure to reindex after your changes are complete. You may want to set up a schedule to do this automatically, or just use the regular SQL search instead.