Thumbnail error generation

[AdieB]

I have looked through the forum but cannot find a thread that deals directly with this problem. I have recently added a bunch of new products +-600 each with image files consisting of a combination of JPG PNG and BMP. When I upload the the site I get consistent errors, namely, "Thumbnail creation error opening: RG59-BNCCRIMP.jpg "

Now, it appears that it is having a problem opening the JPG file to convert to a thumbnail, but why only on some files?? If I look in my sites/thumbnails folder, all of the working JPG are there, ie, it is only converting some of them. I first thought it was a naming convention, but that is not the case.
Any ideas appreciated.
Check out attached file...

[NormanRouxel]

This isn't Actinic directly, but the Advanced Guide article "Automatically Rescale Your Product Images to a Certain Size". Looks like some of your JPEG's cannot be opened by PHP. Perhaps they're saved using CMYK instead of RGB.

[AdieB]

They JPG'S work fine if I select the "Standard Image" in layout, but are obviously not sized correctly. So I would imagine then that they would be saved in the correct RGB format. I must be missing something obvious.

[AdieB]

OK, so the images that I used are actually png images saved with a JPG extension. Why that was done I have no idea, but after converting them to JPG using Irfanview(a great freeware tool) problem is solved.