There is one thing that can be tried as a test of what might be wrong with an ASIO driver: after starting Sonar, fire up the task manager and use it to set sonar's CPU affinity to just one of your CPUs**. If that stops the problem, there's a good bet that the ASIO driver has a multiple-CPU race condition.
It is even possible that some DAW software DOESN'T exhibit the race condition, but not because that DAW is "better", just "different" in how it accesses the ASIO API.
(** Right-click on Sonar's image name and click on "set affinity ..." then uncheck all but one CPU. Naturally, this is not a good workaround because it uses only allows Sonar to use one CPU.)