HTTP Error when uploading images

Hi, I can’t upload images anymore. During the “crunching” I get a red HTTP error message. Then if I look at my Image Library, the images actually do show up in the Library but they are unusable because the size radio button is set to Large with no other option. And instead of the large size saying 2400×2400, it says 0 X 0. (I normally use Medium size). I have been uploading images like this for the past 18 months and I’m not doing anything differently. Any ideas what is wrong? I’ve also tried other browsers and a different upload plugin.

Thanks for any help!
Dennis