I would use the ftp function on the HD24 to transfer audio tracks to and from the computer. You only need a NIC and some Cat.5 cable with a crossover adapter cable at one end to do this. It is very reliable and bulletproof.
If you need to reference midi tracks that were create in Sonar while recording audio tracks on the HD24, export your midi tracks to audio tracks in Sonar, then transfer them to the HD24, record your other audio tracks on the HD24, then transfer them to the computer, then import them into your Sonar project. We do this at the studio all the time and it works quite well. The ftp transfers are a bit slow, but the data transferred is sample accurate, and enjoys the benefits of data reliability that ftp offers as compared to a real time transfer of audio.
Ed