Strange sound problem I haven't seen reported on ubuntu forums yet

Hello,

I have a strange sound problem with gcompris only. I'm losing my reputation in front of my kids because it was working, and then gcompris somehow lost almost all of its sounds, except for Tuxpaint, which is still chiming.

I installed an ubuntu hardy heron lts from scratch with 2.6.24-19-generic kernel, the newest that time. Everything worked flawlessly right out of the box, including sound as well, even with gcompris. Gcompris was configured with the sounds package of our language (Hungarian, if that matters.) Kids fell in love with the computer, mainly because of gcompris, and partially because the familiar voices to them.

I went forward to 2.6.24-21-server kernel (4GB RAM) but can boot up the old one anytime if you like for troubleshooting. I also accepted some recommended upgrade packages that bubbled up from time to time.

After a month of this kind of usage, sound suddenly disappeared from gcompris almost entirely, only TuxPaint held its sound from the gcompris package. And still, everything else has sound, I can play audio and video files, watch youtube movies in browser, etc. Problem is, I cannot pinpoint neither the exact package that broke this down, nor the exact date, since I'm not playing with gcompris. Kids reported the problem and started to complain about the lost sound.

User privileges are OK, sound settings OK (ALSA, btw), test sound can be heard on the config panel, all users incl. kids can hear sound from Tuxpaint and all the above applications, but not from the rest of gcompris. No sound even after completely reinstalling gcompris.

What did I/autoupdate mess up? No clue by browsing syslog, dmesg etc. The most frustrating it was working like a charm right from the first minute, and then broke down somehow.
Please help, thank in advance.
If you would know my kids, you also would cry for help on a forum. :)
Have a nice day,
  Peter