problem attaching files and uploading avatars

I get the following error message when I try to attach a file to a thread or upload a custom avatar. The files are of valid extensions as set by me in my admin panel (gif jpg png txt zip bmp jpeg).

vBulletin Message
The uploaded file is not a valid GIF or JPG file. Please ensure that it is and try again.

Please help.

[filburt1]

Search and ye shall find, especially at vB.com.

[mojoman]

I did a search, but I couldn't find anything on the subject...

[filburt1]

<a href="http://www.vbulletin.com/forum/showthread.php?threadid=65333&highlight=uploaded+f ile+gif+jpg+avatar" target="_blank">http://www.vbulletin.com/forum/showt...gif+jpg+avatar</a>