Sounds like you might have taken out U202, a common 74LS157 quad flip flop.
Should be easy and cheap enough to find another and replace it.
Any variant like a 74HC157 should work fine as well.
Schematics on the A2000 here if you need them:
http://amiga.serveftp.netCan't remember if it's socketed or not. Hopefully not, those sockets are crap.
And remember not to plug your RS232 cable into the joystick port :-)
