Copied this from another forum, several people claim this works, and it makes sense based on information I found on the Sony website.
I had the exact same problem and I finally found a way to do it!! First you need to start the PS3 in safe mode. If you don't know what safe mode is and how to get into safe mode, here's a link to the Playstation Knowledge Centre that explains everything http://us.playstation.com/support/answer/index.htm
After you're in safe mode, follow the instructions on the screen until you reach the safe mode menu, then choose the second option "Restore Default Settings". This will erase all your settings on the PS3 such as display, sound, time & date, internet settings etc. as well as your PSN account information, but you will NOT lose your PS3 user accounts and all your saved games / trophies will still be there. Then just set everything up again from there, link your PSN accounts to the PS3 user account as well as all the system settings!
You can call Sony support (1-800-345-7669) They can deactivate accounts over the phone, but only once every 6 months. Or you can also use there website and deactivate accounts. So you don't actually need to even be on a PlayStation.
Also if ur accounts on numerous PlayStations you can't download on all of them because the transaction management is disabled. You can call Sony and have the activate it. Im pretty sure accounts can be on more then 2 PlayStations now. At 1st it was unlimited how many PlayStations ur account can be on. Then because of gameshare Sony changed it. But with the release of the PS4 they changed it back so it's unlimited again.