Kaffeine sound Error Message

I just installed Ubuntu 6.06 and it is great. One problem is playing DVD's. When I try to play a DVD (unencrypted), I get the error message "Audio output unavailable. Device is busy." (DVD's play in Windows). I have system sounds and if I play a CD, I have sound. Kaffeine is the only movie player loaded. I have tried other movie players and the same results.  I am running an AMD 64 bit computer with 2GB of memory, and a Sound Blaster Extigy external sound card. Any input would be greatly appreciated.