You were reaching the maximum total amount of storage for uploaded images which was 500k. This was meant for avatars and sigs and such. Members were expected to post links to images hosted on image sites. This is a holdover from when the forums were active and if members had used forum attachments the site would have quickly run out of disk space. I guess we can relax that some. I've increased it to 50mb total and 300k for individual images. If you, or others, still find this limiting I can increase it some more.