AU Instruments dont produce sound in host? Help?

[nicksen]

Hello everyone!
I have a problem with opening SB-instruments in Logic Pro 9 and also in Garageband. They are recognized and can be opened by the host, but for some reason they do not produce any sound. (The other Logic-instruments are all working and I do get normal MIDI input) The effects-plugins from SB are also all working perfectly fine.
Does anybody know where this comes from? Similar problems anyone?
Any help is very very much appreciated!
Thank you!