I thought I had a similar problem a few weeks ago. Turns out it was a different problem, but I only figured that after I'd found a solution. Instead of using <input type=image> which I found various problems with presentation on different browsers, you can use the HTML4-friendly (that is, if you're a NS4 fan, it won't work) you can use

<button type=submit name=foo value=bar src=image1.gif alt=whatever>
[download]

Then check for the buttons name and value in whichever way your script likes.

the hatter