Hmm you can't even deactivate? google has many results for that error code some have shared accounts, many seem to be legitimate problems with no solution from sony support i think 80029780 stands for too many activations 5/5.
The solution to this is a simple one don't sign in to PSN or access your downloads for 3 days, some go as far as to not use the PS3 at all for 3 days.
The other solution is a little more hassle, create a subuser on your PS3, signup for PSN again and use that to activate your PSP while its on 5.50 GEN D3 but obviously this doesn't solve the problem like solution 1 it just works around it.
My final suggestion and id do this after the above as a last resort. Access the PSP flash and copy act.dat to your memory stick/pc, delete act.dat within your flash and trying again. Im not sure of any problems involved with doing this but im sure you could put it back or use a pandora incase of problems.
Really hope this helps you, if it doesn't well let us know in a few days
