iTunes not working anymore while using screen in Target Mode

Hi, I use this feature a lot when working from home, as my company laptop is only 12.5" it's nice with the 27" screen. This has always worked out great, but recently (not sure if it started after Moutain Lion upgrade), I'm not anymore able to listen to my iTunes music (running in the background), when moving to "target display mode".

Immediately after pressing cmd+F2, and moving to external mode, the music starts skipping...

It happens with iTunes, Spotify, MPlayerX...

I tried to turn off "always put harddrives to sleep while possible" but this didn't help.

I tried to listen to music stored on different HDDs, didn't help.

Anyone found a fix, or need to wait for new OS update?

Thanks,

Seb