403 Error when uploading from web page

Gallery version (not just "2"): 2.3
PHP version (e.g. 5.1.6): 5.2.9
PHPInfo Link (see FAQ): http://x.poppslounge.com/phpinfo.php
Webserver (e.g. Apache 1.3.33): Apache 2.2.11
Database (e.g. MySql 5.0.32): 5.1.30
Activated toolkits (e.g. NetPbm, GD): ArchiveUpload, Exif, Getid3, LinkItemToolkit, NetPBM, Thumbnail, Gd, ImageMagick
Operating system (e.g. Linux): Linux
Browser (e.g. Firefox 2.0): Firefox 3.5

So, recently whenever I try to upload a file using the "Add Items > From Web Page" tab, I receive a 403 error from my server as soon as I press the "Find Files" button. At first I thought I was actually getting the error from the site I was uploading images from, but I get the same error uploading from a local directory with no hotlinking protection. I never had a problem with this before, and all of the sudden I got this 403 error that happens every single time now. Every other upload method is still working, however. What's really weird is that the 403 error doesn't show up in my server's error log. It's as if something from Gallery is directing me straight to the error file.

The only things I can think of that I changed before this error started happening are:
- Modified the URL rewrite to include the rewriting for keyword albums.
- Disabled square thumbnails module.
- Added an IP to my servers IP Deny list.

Any help would be greatly appreciated! Thank you!

Thanks for the reply.

I disabled the URL rewrite and used matrix theme but the problem is still happening. That theme came with the distribution I downloaded off of this website and I didn't make any customizations to it. The upload from web page never had a problem with it before, anyways.
I have also tried uninstalling and reinstalling the web upload plugin.

That isn't the link to my live gallery, just a test one that I have, hosted on the same server. I installed it as a fresh install to see if it did the same thing. And yes, it does.

pics.poppslounge.com is the main site, which, as I said, I set to Matrix and the problem persists. So what customizations are we talking about then because I haven't downloaded anything other than what was released from this website?

I'll just go without upload from web.