I have a media centre using MythTV that has an onboard sound chip (nVidia MCP73) and a Creative Labs X-Fi Titanium card. The internal sound works fine, but the X-Fi has a very quiet centre and LFE channel when using any of the 5.1 options. Using 5.0 the centre channel is fine and using 7.1 the levels are fine.

I'm not 100% sure, but I think this started after upgrading Lucid -> Maverick -> Natty.

Any idea what is happening here?