Well said, Cakey -
I've just come to this post, to note something rather more serious than having to log in monce a week. It's taken me 20 mins to fix it, so i'll describe the problem, to save others the time:
When I went to log into TMC, i got nothing. It just returned me to the login dialog again. And again.
So, I tried a few other sites - gmail etc. All not working. Either getting stuck in redirect loops, or doing nothing at all.
I'm running windows XP (slightly tweaked), so i set about fixing the problem. It was soon obvious that my browser wasn't accepting any cookies. I cleared the cache. Tried other browsers (IE, firefox - first browser is Chrome). Did a system restore, rebooted, all to no improvement.
Some googling later - it turns out i had accidentally changed the month, in the system clock. I was discussing my movements, and had no internet connection, so rather than pull up google calendar i had to use the system one. I altered the month - and didn't alter it back. Bang - all cookies cease to work.
Reset the clock, reboot - all fixed !!!