Error - No Devices (Audio)

Good afternoon everybody,

first at all I have to apologize for my bad english - I'am not native

After installing XBMCbuntu 12.0 RC3 everything was working well. But after a few days and restarts there are no more audio-devices (Error - no devices found). This is already the 2nd time it happened after re-installing the whole system. Any suggestion how to fix this problem?

The system's specs:

ASUS BB S1-AT5NM10E
4GB RAM
Intel 520 SSD 128GB
Onkyo AVR TX-SR 308

Thank you in advance!

brgds
kos90