No sound with snd_hda_intel on T61, bug fix has already been proposed, but as long as xen-sources are using an older kernel version it would be nice to include patch in ebuild (version >= 2.6.23 are supposed to solve the problem).
bug confirmed, patch works perfectly for me (even with USB and nvidia drivers):
Steps to Reproduce:
Dropped version. Try .29 or .31 :)