NEED HELP uploading more pictures "Security Token Problem"

[72 Blazer CST]

I had started a thread on my blazer build and am having problems uploading more pictures to my thread. When I hit post reply, after I type my thread and try to add pics I hit browse and select 4 or 5 pictures. Then I hit upload, it does its thing for a little while and then gives me this message. "Your submission could not be processed because a security token was missing". I want to buy a membership to this site but I want to make sure it is going to work for me first. I have emailed the site twice but have gotten no response. Any help or ideas would be appreciated. Thanks in advance!