This is not an ubercart bug, but I think we should help get this resolved as it effects ubercart rarely but severely.

Here's how you replicate this bug:

1. Take a bunch of product shots.
2. Create a product and upload IMG_0001.jpg into the product Image field. Call this product #1.
3. Visit product #1's page.
4. Delete product #1.
5. Wipe your digital camera and take more product shots.
6. Create a product and upload IMG_0001.jpg (which is a new product) into the product Image field. Call this product #2.
7. Visit product #2 page.

You'll notice that product #2 displays product #1's image.

Why?
It's an imagecache bug. Imagecache does not delete old caches when an image is deleted or updated with the same name.

This bug is outlined here: http://drupal.org/node/362356

How'd you find out
I had a client upload 200+ products over the course of a couple photo shoots. Every time he had a new photo shoot his camera photo numbers would reset the filenames, this created a bunch of duplicate filenames. He deleted some products through out the photo shoots and this caused us to notice the bug.

How can we fix it, so that Ubercart isn't broken?
Come over to the imagecache issue queue and request that the bug get fixed for the next release. If anyone could supply a patch that would solve the problem for Imagefield that would be superb as well.

Imagecache Issue Report: http://drupal.org/node/362356

Temporary solutions
Flush imagecache after each time you create a new image or don't use duplicate filenames.