I am beginning to think this may be a yahoo problem. I would, however, still appreciate any help anyone might offer since yahell's tech support is worse than useless, from my experience.
Something I didn't think to mention last night---I was so frustrated that I was ready to bang my head on the wall---is that I did have the last version of zencart installed on my site and it worked fine for a month or so except for one little glitch in the 'contact us' email. Worked wonderfully, I was very pleased with it.
Then yahoo attacked, lol. I activated Frontpage extensions and all my php scripts quit working. I deactivated them and it didn't fix it. After spending a total of about 6 hours on the phone with yahell tech support someone finally told me I needed to delete every single file in my domain and start totally over from scratch in order for Frontpage and the damage it did to be completely wiped out. I did. Then I installed the most current version of Zencart and had the no-image problem.
I thought about this last night, the older version working fine till frontpage, and I decided to install it in a different directory from the new version and see if it worked, since it worked fine before. And it now has the same problem of not uploading images or sql patches.
Does this sound like a yahoo problem? Could it be something in my compute, since it seems to be tied to uploading stuff from my own hard drive? I'm at my wits end.