403 Forbidden on Profile Image Uploads except for Super User (CB 2.0.4)

For some reason whenever I attempt to upload either a canvas or portrait image into the profile of a non-Super User, after the upload finishes I get a "403 Forbidden" screen. I've increased the PHP memory limit, increased the image size maximums in the CB configuration, which allows me to upload pretty large panoramic images into the Super User profile, but not into a "Registered" user profile. Clearly this is a permissions issue, but I have no idea which permission I need to change to resolve this. Does anyone else know?

Thanks in advance.

EDIT: Looks like I can't select a gallery image either. Same error (403).

Just bumping this up since there's been no response. The issue is still present. If anyone knows the secret to resolving this I'd appreciate you sharing. Thanks!

Bruce