I am having the same problem.  I connect and start running around, and within 30 seconds I get the "Server is not responding, try back in 5 minutes" message.  However, my situation is even stranger.  I have been playing PS over the last week religiously.  I was even playing it a few hours before I left for work.  But when I came home, I couldn't connect (or stay connected).  That was almost 4 hours ago now.  I have been constantly checking the server status, and it claims to running fine with 80+ users. 

The only thing I changed between the many many hours it worked fine and now was adjusting some settings in pssetup.  Specifically, I tried using a different resolution and adjusted downwards the quality / speed options.  Even though I changed them back, nothing.  Could they have altered the config file in such a way as to not be fixed when returning to default settings? 

Just in case: I am running a powerbook g4 (1.25) with 768 ram, ati radeon 9600 (64MB), and OS X 10.4.8.