No sound

My friend has a

Modelnavn: iMac
Model-id: iMac4,1
Processorname: Intel Core Duo
Processorspeed: 2 GHz
Number processorer: 1
Number cores: 2
L2-buffer: 2 MB
memory: 2 GB
Busspeed: 667 MHz
SMC-version (system): 1.1f5

running os x 10.5.8

with a dmesg we get this output
t for: 00:22:4f:81:9c:6e MAC AUTH succeeded
AirPort: Link Up on en1
WLC_E_COUNTRY_CODE_CHANGED
en1: 802.11d country code set to 'AT'.
en1: Supported channels 1 2 3 4 5 6 7 8 9 10 11 12 13 36 40 44 48 52 56 60 64 100 104 108 112 116 120 124 128 132 136 140
AirPort: No beacon for too long time
AirPort: Link Down on en1
Auth result for: 00:22:4f:81:9c:6e No Ack
Auth result for: 00:22:4f:81:9c:6e No Ack
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
Auth result for: 00:22:4f:81:9c:6e No Ack
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
AirPort: Link Up on en1
AirPort: Roam (DeAuth/DisAssoc)
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
AirPort: No beacon for too long time
AirPort: Link Down on en1
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
AirPort: Link Up on en1
AirPort: No beacon for too long time
AirPort: Link Down on en1
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
AirPort: Link Up on en1
AirPort: No beacon for too long time
AirPort: Link Down on en1
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
AirPort: Link Up on en1
AirPort: No beacon for too long time
AirPort: Link Down on en1
Auth result for: 00:22:4f:81:9c:6e No Ack
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
AirPort: Link Up on en1
AirPort: No beacon for too long time
AirPort: Link Down on en1
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
AirPort: Link Up on en1
Ethernet [AppleYukon2]: Link up on en0, 100-Megabit, Full-duplex, Symmetric flow-control, Debug [796d,6d0c,05e1,0200,45e1,4000]
AirPort: No beacon for too long time
AirPort: Link Down on en1
Auth result for: 00:22:4f:81:9c:6e No Ack
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
Auth result for: 00:22:4f:81:9c:6e No Ack
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
AirPort: Link Up on en1
AirPort: No beacon for too long time
AirPort: Link Down on en1
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
AirPort: Link Up on en1
AirPort: No beacon for too long time
AirPort: Link Down on en1
Auth result for: 00:22:4f:81:9c:6e MAC AUTH succeeded
Auth result for: 00:22:4f:81:9c:6e Unsolicited Auth
AirPort: Link Up on en1
unknown SIGSEGV code 0

He has no sound after upgrading his os x version. And we dont understand why. Anyone here who can help us?

Thanks on advance
Kind Regards

What is checked in the Sound preferences pane? Where are the sliders set?