Systembase has been the recommended USB to Serial Adapter for use in programming the Rabbit BL2600 for many years.
They have gone through several design changes, and recently this year they have changed to a new version, designated Ver4.0 on their sticker, and they are no longer working with the RFU 2.50 utility.
I connect to my BL2600 using RS-232, and that works with the cable, I can communicate with it, however the programming does not work.
I have tried updating drivers from the included CD, to Windows Update's FTDI Drivers, to the SystemBase drivers on their website. None work.
Does not work on Windows 7 64 bit, or WinXP.