The problem is a security fix that was added to the forum in one of the forum updates. I can be caused by a couple of things.
- ISPs that change ip addresses on the fly
- AOL Browser
I can tell that from the looks of it between the three people that posted here that one maybe because of AOL, and the other maybe because of their ISP changing IPs.
Here are some options you can try:
1. Try using Firefox over IE or the AOL browser.
2. If you are using any web acceleration software, turn it off completely or just for this site. (this can be part of your firwall or antivirus software) Things like googles web accelerator and similar programs.
3. Some people have had luck with using the remember me checkbox when logging in, but I would only use this as a last resort.