Are you plugged into a powered port?
Also, are you sure the dropouts are related to the cable length and not to some audio issue on the computer?
Please list your:
1. Driver Mode in Sonar
2. Recording Bit-Depth in Sonar
3. Sample Rate in Sonar
4. Reported latency values in Sonar
5. Please indicate the type of audio interface you are using
6. Audio interface Sample Rate and ASIO Buffer Size
7. Sonar Buffers.
I regularly use really long midi cables without trouble - don't know if they are over 30', but certainly are close.
Bob Bone