.NET 2005, Serial Port, Dispose Windows CE?

I write program for Windows CE that should work with Serial ports. I use object System.IO.Ports.SerialPort. Everything works well but when I close program and open it again, I receive error: Port is in use! At the end I write:

port.close()
port.dispose()

And If I add this:System.GC.collect() than everything begins to work But problem is that computer gets stuck when garbage collector is called for each port. If I tried to use collector somewhere else, it doesnt "collect" ports and they look like used if program starts again.