Compact Framework sockets, performance

I am sending a lot (hundreds) of files from a desktop app to a PocketPC app using Sockets and NetworkStreams. Both are written in VB.NET. The parameters which identify the file transfers pass from app to app over a "control" connection. Each file transfer itself runs over its own "Data" connection. My problem is performance. The first transfer gets a rate of 60+K/sec, but all subsequent transfers get no better than 2k/sec. I am closing the sockets, but not sure if I should dispose or finalize them, could this be the problem? Also, I have had to limit the maximum number of concurrent transfers to less than ten, otherwise ActiveSync 3.8 crashes with a 10055 (no more sockets available) error. Any suggestions welcome…
Ivan