Michael,
Drinking my last beer of the day, so may or may not pass on cardinal information.
There should be no limitation in Sonar by design to use the ASIO4all driver. Saddest, worse case scenerio would be trying to wrap a generic motherboard Realtek soundcard driver with ASIO to get a few less millisec of latency. Lipstick on a pig thing.
Otherwise, your specific soundcard may not recognize ASIO4all, but require a hardware specific driver package. Sonar is open minded and up to speed, wanting to harness anything you got on your motherboard or in a Pci slot if the hardware supports it. Problem is likely downstream and nothing to do with any limitation imposed by Sonar.
John
edit. Uh, fly off the handle too often before reading the post in depth. Michael, was not your problem.