A couple of other things I did, but probably didn't help with the solution... I temporarily turned off the "protected mode" of operation for Internet Explorer. Restarted Internet Explorer and looked at the cookies on the PC using IE Tools. You will find they are now in a folder called "Low", apparently for low security. I did find a cookie there for www.thechipboard.com that was not visible when I was in Protected Mode. I deleted this cookie, restarted Internet Explorer, and then turned Protected Mode on again. I browsed TheChipBoard, and did the "Mark all messages read" thing from the board. When I then restarted IE and returned to the board, all was well.

None of these additional things should cause a problem so I recommend you try them if you are still having a cookie problem.

If you have properly implemented David's fix, you should have www.thechipboard.com on your list of Trusted Sites, and when you view the browser screen, you should see at the bottom "Unknown Zone (Mixed) | Protected Mode: On". I'm assuming you're using the same software as I am, which is Windows 7 and IE version 8. If not, you might consider upgrading the Windows software to Windows 7 and Internet Explorer to version 8 (it's free).

Good Luck!