this ins’t a php issue, your form has no submit button:
<input type="image" src="images/submit-button.jpg" name="Submit" id="submit" value="Submit" />
I’m surprised it submits in any browser.
Heh must be some vbulletin bug.
eh? that post was a reply to another one by someone else
7 hat do
Inputs of type ‘image’ always function as submit buttons. It also sends the coordinates where the image was clicked.
Doesn’t explain why vBulletin is making new posts from your answers to someone else. Weird 
the odd thing is that it was in the original topic until yesterday!
just to prove i’m not going mad, the original topic is here: http://www.sitepoint.com/forums/showthread.php?t=697942