Just over two weeks ago there were reports of WipEout HD crashing/freezing and some partially-working DIY-style fixes.
The good news is, WipEout HD has now been patched in order to fix the common game freezing problem among PSN users with over 50 friends.
Currently this patch is available for the European version only, though it is expected to go live in America very soon. The patch notes, which can be retrieved from within the game, state that your save file needs to be deleted after the patch has been installed for the fix to take affect.
This means your lap times, team loyalties and other single-player stats and options will be lost. Your trophies and leaderboard scores, however, won't be lost.
If you've been sidestepping the issue by playing whilst signed out of the PSN, starting again is no doubt quite an annoyance. Don't get too upset, though, at least you can now play online with your friends. More PlayStation 3 News...