No files playable through UPnP

[Jonhoo]

Hi all,

After a recent upgrade to 3.2.3, my Xbox 360 can no longer play media files from TwonkyMedia on my Qnap TS-410. It can see all the files and browse through them, but none of the files are playable (even those I have played before and know to be working).
Everything else seems to be working fine after resolving some earlier issues (viewtopic.php?f=189&t=27491, viewtopic.php?f=50&t=27356).
I can even go to the twonkymedia web interface and browse the files and download them from there and they work fine.

Any ideas as to why UPnP is now suddenly broken?
Jon