Hello,
I Just got an RFM last weekend as well. I managed to update the software to 1.5 using a Dell laptop with Windows XP. Laptop does not have a DB9 serial port. I used a USB port. I purchased the following cable from Amazon.
StarTech.com 1 Port USB to Null Modem RS232 DB9 Serial DCE Adapter Cable with FTDI, Black (ICUSB232FTN ) Link follows:
http://www.amazon.com/gp/product/B008634VJY/ref=oh_details_o01_s00_i00
Installed the software that came with it set port to Com1. First time I tried it did not work. So dug out a pc running windows 98 and tried that with a serial null modem cable.
StarTech.com 10-Feet DB9 RS232 Serial Null Modem Cable F/F (SCNM9FF) Link Follows:
http://www.amazon.com/gp/product/B00006B8BJ/ref=oh_details_o00_s00_i00
This did not work either. Looked inside the RFM computer box and the serial cable from the back of the RFM computer box that plugs into the motherboard was installed backwards. Changed it and both cables and computers now worked to update the software. For me both worked. Hope this helps and saves someone some time.
Happy Holidays
Andy Limerick