I have a Garmin 60cx due to be delivered tomorrow. I purchased it from Buy.com for $313 including shipping. The 60c(s)x get very good reviews here. I can't wait to get mine.
I suspect your software doesn't play well with high numbered COM ports. I had a similar problem and changed the COM port my USB to serial adapter uses from COM30 to COM2 and that solved the problem.
I also had trouble using a USB to serial adapter with easyGPS. I discovered that configuring my adapter to use a low number COM port (COM2) fixed the problem.