[Ozymandyus]

Carnage, I have SStabs vbsoporte, auto-backup, and vsa Chatbox installed, along with dartho's mobile styles. I can't tell you specifically if any of those are causing conflicts, but I can't tie any issues to them. Upgrading to 4.0.5 helped a great deal with my issues, but I was still seeing a lot of error messages on post and the occasional double. Turning off your mod alleviated this problem. I have a hard time living without it, but have managed to replicate the functionality by turning off the vb CMS and using a vbadvanced portal instead.

Only other tidbit I can contribute is that the double posting happens FAR more often in Internet Explorer 8 than in any other browser, according to my user reports. It seems to happen much less frequently in Mozilla and Webkit browsers, but doesn't completely go away.