11.0.5721.5280
On XP SP3 Home - italian.
It was installed from Windows Update.
I tried to uninstall, rolled back to WMP9, no problem with 9, re-installed 11, red again.
About AVAST guys, I am not much confident.
Besides, not their fault but it is rather annoying being either ignored or answered like "change your OS with Win7" or "use VLC".
Also because it takes time to understand an issue with Media Player is related to the antivirus.