Midi Issue With Os X 10.3.9


I've recently started using Nuendo on my Mac and I'm a real digital recording rookie, so maybe this is a dumb rookie questio, but here goes. I've installed a drum module and Sampletank 2 LE to trigger the drum sounds - so far so good. Because it's easier to "play" the drums with a keyboard than by clicking with the mouse on Sampletank's keyboard, I hooked up an old keyboard through my M-Audio Firewire 410 A/D converter, but when I opened Nuendo I got the message "could not connect to CoreMidi. You should restart your system", and I can't get the keyboard to trigger the drum module sounds at all. This message never came up before I installed Sampletank and Mac OS help doesn't say anything at all about CoreMidi. Help!