Logic and korg X50 problem

Hi

I'm using the X50 as a controller via USB and all good when loading plug -ins eg ESP. When I load the X50 plug-in editor I get no audio and Logic runs at a snails pace. I also get a continous midi exclusive signal no.66. This was working fine a couple of weeks ago. Any ideas? Thanks.

G4,1 ghz dual.1gb ram Mac OS X (10.4.7) logic 7.1.1,korg N1,unitor 8,01v