A new firmware release 1.1.1 is available for Frankfurt RS-232. This is a bug fix release and it fixes a problem that occurs sometimes when sending frames with maximum length. Typically this happens when bootloading a device over the VSCP daemon.
The new firmware is available here.
Manual and instructions on how to update the firmware is here.
As a general note please enable hardware handshake whenever possible using the Frankfurt RS-232 module for bootloading.