Nobody else seems to be keen on answering this question, and it was starting to bother me.
So I looked in preferences and found that under the "Web" tab, there is "Automatically check for newly published albums" setting, checked by default.
Looks like you can un-check it and the problem goes away. Of course that feature does, too, but since I do all my photo publishing through Aperture it doesn't bother me.
I suspect the problem is an intermittent connection with Facebook, but I'm a little surprised since Facebook has always been one of the web's most reliable sites, and whatever's happening isn't impacting my regular Facebook browsing at all.
Hope that helps.
D