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ValveTime.co.uk | Valve News, Forums, Steam
It's been talked about in threads, but I thought it aws worth creating a thread for all to see.
Basically a cookie is created that prevents access to the forums for a couple of hours.
Before you flame valve, remember that the forums were destroyed by traffic, so they've obviously put this in to keep the forums up - better limited access than none at all.
So clear your cookies and you should be able to log in.