Okay, I got it fixed, as you've already noticed
It turns out the host installed some extra security that had a problem w/ a PHP include I added... I ended up paying $50 for support services I didn't need. Had I checked w/ the host last week, all of this would have been avoided. Unfortunately, I was so short on time, I thought I would get the fastest result from SMF directly - apparently it had nothing to do with them. Now I know & hopefully nothing like this will happen again!
Thank you for your patience!
Now, on a similar note - since so many people seem to prefer a different theme over this one, I'll be working on customizing those and offering a choice. It may take some time, but I will work on it ASAP