I am curious - why are you using the WDM drivers for your interface, rather than ASIO?
I checked the web site for the interface, and indeed there are ASIO drivers available for it. I generally attempt to install and use ASIO drivers first, for any audio interface I am using, however some folks do have better results when using WDM. It is usually wise to try the ASIO driver mode, if issues with WDM, and also to try WDM driver mode if issues with ASIO. One or the other should result in good performance and stability.
When you go into Preferences, you may need to remove the check box for the audio interface, in order for you to be able to select the ASIO driver mode.
The ASIO driver mode also will use a parameter that you need to set, for adjusting the size of a buffer for the interface to process the signal. It is usually called ASIO Buffer Size, or sometimes the interface will control that buffer with a slider, or will have you pick from a number of samples - different manufacturers use different methods of controlling the size of the ASIO Buffer.
I mention this because for the rest of time you will need to switch the size of that ASIO Buffer, depending on what kind of processing you are doing in Sonar. When tracking/recording, you need the ASIO Buffer Size to be fairly small, or you will hear a lag between when you play a note and when you hear it back. On the other side of ot, when you have finished recording and move on to mixing/mastering, you will almost always want to jack up that ASIO Buffer Size to be very large - this is to accommodate effects that often need the larger buffer size for the type of processing they do, like convoluted reverbs and effects that use look-ahead processing.
SOOOOO - I generally use a sample rate of 48 k, and an ASIO Buffer Size of 128 for recording, and then when I move to mixing/mastering, I jack up the ASIO Buffer Size to 1024 or 2048. The high latency that comes from the big ASIO Buffer Size doesn't matter when mixing, because you aren't trying to record tracks while mixing.
So, I suggest you try the ASIO driver mode, with the above settings and report back with your results. It may not fix things for you, but is certainly a reasonable place to start.
Bob Bone