YouTube won't keep me logged in...

It just started today. For some reason YouTube won't keep me logged in. I can sign in just fine, I can surf fine, but If I close Firefox for whatever reason YouTube logs me out for whatever reason. I thought it was malware so I did a full scan with my primary anti virus and anti spyware they came up empty, I restarted the PC that fixed the problem but now it's back. I had trouble upgrading my Yahoo Toolbar earlier as well but that problem went away when I restarted Vista. All other websites are working fine. So is this a YouTube glitch or something else?

 

I think I found out what was causing the problem. I think when I suffered the failed update of Yahoo Toolbar it messed up Firefox's cookies.sqlite file. I don't know how. I don't know why. But I deleted the file and was able to close firefox and stay logged into YouTube and GameFAQs.com so I'm hoping I found the problem and fixed it.