Problem using Cubase with iMic, sound doesn't play right Options

[brome]

I recently bought an iMic for my powerbook, but I encounterd problems using it with Cubase. I use :

- Powerbook Titanium G4/400 256 Mo
- OS 9.1
- Cubase VST 32/5
- an iMic, connected via USB

When the iMic is connected, the 'VST Performance' window shows a red light, to signal that the processor usage is too high. But the gauge only shows 5 to 30 %.
And when I try to play a song, no matter how many tracks there is or if there are effects applied, the sound doesn't play right : the sound is cut every 1 or 2 seconds, as if someone was playing with the MUTE button !

Does anyone know what could be the problem ?

Thanks,

[brome]

I've made some more experiments with mi iMic last week end.

I've de-activated all extensions that could interfer with Cubase.
Cubase now almost plays the sound normally, but there is still a problem when I record some audio.

Other applications can use the iMic correctly without problems (I've tested with Feltip Sound Studio for example and everything is OK). But when recording with Cubase, the sound volume is very low, and each access (read or write) to the hard disk produces an awful noise, which is recorded too !

Is there any settings I should check in the Cubase preferences ? What am I doing wrong ?

Thanks to anyone who can help !