grungoo
Thanks for the tips, everyone. I've removed ASIO4ALL, and installed the latest driver for Scarlett 2i2. Now I'm getting an Audio Device Error: "The following drivers either do not support the current audio format, or are in use by another application."
I am using a laptop, so I'm not sure if that's the problem.
Are you definitely using the ASIO drivers, or WDM? The reason why I ask is you can aggregate multiple interfaces with WDM, but usually not with ASIO. It sounds to me like Windows is grabbing the interface for its own nefarious needs before Sonar gets the chance.
As an aside, it's really unfortunate that Windows makes it so difficult just to set up an effing pro sound card. People shouldn't have to go through all this just to be able to use Sonar. This is one area where the Mac is way ahead; Core Audio is standard, fast, and can aggregate interfaces easily. While I think the Mac's reputation for ease of use has a large amount of hype over substance, audio interfacing is something Apple really got right.