Ok, well this is strange!! Just loaded it up again and my ps3 seems to be working now!!
I am half tempted to see for a third and final time if wipeout HD is going to work!! Am i mad?!
edit: Ok, third time, and it has crashed. DO NOT DOWNLOAD THE UPDATE PEOPLE! YOU HAVE BEEN WARNED!!!
Exactly the same problem here.
Except my HDD didn't report any problem with the harddrive.
I just loaded WipeoutHD to grab the patch.
it got as far as the "autosave information" page, the little arrow spins around a few times, and locks the PS3 solid. Only way to get out of it, is to hold the power button for 3 secs, and let it shut down.
Tried again, crash.
Tried again, crash.
I just saved my savegame on a usb drive, and was about to try to load the game again with no profiledata, and see if that's the problem, seeing as it crashes on the autosave screen. But if others are having problems, I may just leave it, and see if a new patch comes out in a day or two.
If I have to delete my savegame to continue, I won't play it again anyway. I'm on the very final section of levels before the end.
Vin.
EDIT: by the way, I loaded Wipeout HD earlier this afternoon, to check for the patch, before it was live, and it worked fine then, it's definitely the update that's broken it. I've never had 50 people in my friendslist either, which was a reported bug for their last update. I can't even find the update data to delete. So, I'll just leave it now, and hope another update comes out to fix it.
EDIT2: Just checked the link in the OP, seems everybodys is borked.
http://blog.us.playstation.com/2009/04/07/wipeout-hd-update-racing-to-psn/comment-page-3/#comments
I'm happy actually, if it were just a couple of us, who knows what would happen.
if everybody's wipeout HD breaks after the update, more chance of getting a fix patch soon!
It does state there though, that deleting your savegame will fix it, which is what I'd wondered.
I'll leave it for now though, see if a fix comes out. If nothing's done in a week or so, I guess I'll have to do that.
EDIT: Workaround
Here is s work around guys. Thanks to Mazyx for part of the solution. If you signout of the PSN before loading up the game you can get by the loading screen. YOu can then sign on to the network if you go online and no issues. Then if you change your settings or something that requires a auto system save the save file will be updated and then the freezing should stop. I quit the game and started it up again logged into PSN this time no issues.
my ps3!!!! nooooooooo!! 
Not ideal and they will still have to fix it because they can't expect everyone to go and do the same thing!!
