No input / output sound devices, no startup chime
I have got a (second) MacBook 17" 2.93 GHz C2D unibody from early 2009.
Last days I noticed, that the sound devices (input / output) disappeared in preferences pane.
Also I do not have any startup chime.
I reset NVRAM / PRAM, SMC and also I took off the battery and interestingly, this helped from time to time. Lets say 2 out of 5 attempts to get it back to life are successful.
Also I repaired file system permissions.
I checked it by installing Win7 with boot camp, but also the sound devices do not appear in Windows.
It seems to be the fact, that if I do not switch on the MacBook for 1 or 2 days (or even longer) and switch it on then, the sound devices appear again; also sometimes the volume keys on the keyboard do react very, very slow (took about 2 or 3 seconds until I get the sign on screen after pressing).
I tried it by installing Snow Leopard, 10.6.8, and Mountain Lion, 10.8.4 - no difference at all.
Is this a good question?