Have you repaired permissions? After upgrading, that's a must-do. Have you emptied your cache as well? That seems to help sometimes.
And finally, have you tried connecting with a different browser, such as IE? If you still have trouble connecting, it could be the network signal (I have broadband via AirPort and it can get a bit sluggish at heavy-usage times of the day).
And finally, sometimes opening and quitting Safari, then restarting the Mac seems to give it enough of a kick to get back to connecting at a normal rate of speed.