I didn't try the online mode, but booting GT5 when being connected to PSN takes ages.
If PD moves its online department to Fukuoka, I think they move its servers, too.
Maybe PD moves the servers step by step, so GT5 doesn't totaly loose its online functionality, but for the price of a bad connection for a while.
I don't know, but this could explain the bad connection at the moment.