Forum Strange problem - .png changing to .jpg
 

I recently upraded a medium sized site to vb4. As part of the upgrade process I initiated a contest for users to come up with a new banner for the site. One of the rules of the contest was that the submissions be in .png format.

Now, all of my users have been submitting them in .png format. I know that now, because when they are submitted I look at them, and they are .png files. However, at some point later, maybe six hours or so, they are magically transformed into .jpg files. I'm at a loss on this. I've been chasing my tail for the last three days trying to figure out what is going on. I don't know if it's a server side setting (checked both GD and ImageMagick with the same results) or a vBulletin cron that I just cant find... but I'm about at my wits end.

It's not happening on all files, which makes it even more madenning. I've tested this myself by uploading 8 .png files to the server through the normal vb4 upload routine. I've placed these files in a forum that only I have access to. All of them were .png files when checked two hours later, but six hours later six of them were .jpg files and two of them were still .png files. 48 hours later I still have six .jpg files and two .png files. This is costing me a lot of sleep. Does anybody have a clue?