[MacDV] Voice over in imovie

[Robert Green]

I have an intel core duo imac running 10.4.9 with imovie 6.0.3. I  
purchased a griffin imic to do voice overs in imovie. When I plug in  
the mic and select it in system preferences it seems to be working  
because I can see the audio level indicator moving when I speak. When  
I hit the record button to do the voice over the spinning rainbow  
appears and stays. I have to force quit imovie. This happens when I  
select the internal mic or the imic. Any suggestions as to the problem?
Thanks
Rob