Product Pictures

I'm not sure if this is a template issue or a virtuemart issue. However I seem to be have trouble uploading the product photos. I'm not sure if it is the file size (usually 800x800px or so) or something different. Most of the photos were edited in gimp and saved as jpeg's. They open fine in other viewer/programs. Instead of the product being displayed a downward arrow is displayed.
I should mention that I upload a few successfully but other not, I can't seem to find a rhyme or reason why.

Any thoughts?

Thanks again.

To add to this - It seems if I open the jpeg image in Microsoft Picture Manager then save it as a different name this seems to work. But I'm not sure why? I also just may have been 'lucky'.

Please don't use special characters and space in the image names. Use only english alphabetical letters and numbers.

I will keep this in mind however currently I only use english letters and numbers.

It must be a problem I have with saving in Gimp. Even though I save the image as a jpeg there must be another setting that needs to be changed. Currently this seems to work - modify the image in gimp, save as filename.jpeg, open in microsoft picture manager, save as filename1.jpeg (notice the renaming), and upload to virtuemart. It works fine then.