Blood_Sword = This still sounds like you are right on the line as far as the file size requirement (your file might be rounding its actual number.) Photos, even the exact pixel dimensions can be slightly different file size due to color saturation (a black and white or a low saturated photo will always be a bit smaller than a bright vibrant image.) And files right on the line of size requirements might be digestible by the site's resizer when reloaded individually but just not work on the initial bulk upload.
If you would like though, you can attach the original files in a post in this thread, and I can look at them directly instead of just guessing. ^_^;