[LSU Jonno]

I can, but I'll be out of town until Tuesday. I have a little more troubleshooting to do as well. I'll plan on checking my drivers after reading more stuff about the new AE, although I'm not outputting HD audio so it shouldn't be an issue...

On one HTPC i'm running an AMD fusion machine and outputting sound through HDMI to me TV.
The other HTPC I'm running an AMD 5830 video card with HDMI to my TV but I'm outputting sound via SPDIF to my AVR from the motherboard.

No clue if I'm running microsoft or realtech drivers or what so I'll check that first, upgrade as necessary to OEM drivers and report back with a log on Tuesday.

[LSU Jonno]

Didn't have time to get logs and post before I left to go out of town but I did play with some drivers and have an update.

On my Fusion machine I had a microsoft driver and an AMD HD audio driver installed. I deleted the microsoft driver and kept rolling with the AMD driver and that fixed the issue on that HTPC. Regardless whether I have the "exclusive control" box checked I can now switch between XBMC and WMC flawlessly.

On my other machine its a different story.
CPU: AMD Athlon II X3
Mobo: ASUS 760G/A&V&GbE/Micro ATX Motherboard M4A78LT-M
RAM: 8GB
Video: ATI 5830

I had an AMD HD Audio driver installed for the video card's HDMI port, and a microsoft driver installed for the SPDIF port on the mobo. I uninstalled the microsoft driver and installed the mobo specific driver (VIA Audio Driver V6.0.1.9500). However this didn't fix the problem. I have the same issue that was described by the OP and my original post.

I'll try to post logs on Tuesday when I get back.

[beanaroo]

I can confirm that I too have this problem on my desktop and laptop. It has been present since I tried beta and at the moment I am running the stable 12.0-1 release. I have noticed that the issue occurs on both Debian and Arch based distros.

We cannot launch external programs on our HTPC. This isn't a big problem as exiting xbmc is a workaround.