I have got the same problem, not only on pokerstars, but on all PO supported sites.
Started a week/2 weeks ago, My virus/firewall protection is Telia safe surf (uses an F-Secure license). Have done that for a the last half year with out any problems.
Just prior to the problem I got a warning from Telia (my internet provider) regarding the connection to US sites, relating to this:
The Telia-Cogent Spat Could Ruin the Web For Many - GigaOM
So I just thought that was the reason, but that might have just been a coincidence, thta it happened a the same time.