Category Main Images Not Showing Up

I went to replace my Category Images, and have tried multiple ways, including manual upload, through the FTP client etc but when I deleted the old images and uploaded the new images, only 10 out of 12 work… and it just simply will not upload on the other two categories.

and yes, we have cleared our cache…

any ideas on why this would be happening? Thank you.


Does the problem occur only with certain images?

Yes, I have 12 categories and 2 out of the 10 will not work, or allow me to upload new images.