[All Internet Browser, system]Cookie problem

Greetings!

I am currently having a cookie problem with my computer, which started yesterday, while I was trying to patch up the game LeagueofLegend (I dont know if it is relevant or if it even caused it, but including everything that could be the cause)

I had trouble patching my game and ended up uninstalling LeagueofLegends and Adobe Air, which it uses to run, and then reinstalled, still not working, so I gave up.

Now, on several webpages I frequent, I have troubles log-in in (this problem does not happen all the time on all webpages, even not all the time on the same webpages)

The error I am getting is that I am unable to login, as I need to use a cookie enabled browser.

I am currently using FireFox as my primary browser, now, this is what I have done so far to fix the issue:

-Tried to use IE to login - same error message
-Downloaded and tried Google Chrome -same error message
-Checked and other users are still able to use the webpages just fine
-Checked cookies was enabled in FireFox
-Messed around with settings in firefox, trying out every possible combination I could think off
-Delete all history, cookies and everything in FireFox
-Check cookeis was enabled in IE
-Delete everything in IE
-Check I had latest update of Firefox
-Clear space on c-drive
-Run CC cleaner
-Disable firewalls
-Disable Antivirus
-Disable Antivirus and firewall (Using Norton Anti virus and Windows Firewall, if it is relevant) (and yes, I re-enabled them after I found it changed nothing)
-Reinstalled and got LeagueOfLegends to work again, browsers still have same trouble.
-Running Firefox in admin mode
-Reboot the computer several times
-Deleted my cookies file in the FireFox profile
-Made exemptions to my firewall for the sites in question

I am pretty sure something somehow messed up a kind of global setting on my computer that I dont know about, since it is 3 different browsers suddenly giving the same error messages, but I have no idea what or how to correct it

I am running out of ideas and it is hugely anoying'

The Websites in question are NSFW and hence no names or links are mentioned, but it is safe to conclude nothing was changed on their end and they are still functional for other users

 

Argh, just noticed I forgot my specs, and cant find an edit link, so sorry for double posting:

Windows 7
Windows Firewall
Norton AntiVirus
Firefox 3.6.13 (latest danish version)
And yes, I have checked that my computer time and date is correctly set