Can you be more specific about exactly where it is you're trying to post photos too? We have at least 3 places where you can post photos here: your album (part of your profile), the photo gallery, and individual posts.

What option are you clicking on? Have you tried resizing the photos to be smaller before uploading them (or try to upload a small test image)? Sometimes this error message might be related to your photo's size...

DocJohn