In the event that your ABS modulator has died and you're not up to paying BMW $2500+ for a new one, a viable option is to install a used one from a salvaged bike. Of course, it's helpful to either know it's a good part, or have a money-back gaurantee on the part. Also, it might be wise to steer away from units that have been removed from a bike for several years as the seals can deteriorate.
In any case, make sure the replacement unit has the same BMW part number as your old unit. Close is no good, you need the exact part.
However, unless the replacement modulator came from the same model bike (the same modulator is used on multiple bikes, e.g. R1200C, R1100S, R850R, R1150R, and early K1200RS all use the same part), it will need to recoded. A willing dealer can do this in a few minutes w/ the special BMW tools. The price they charge will be an indication of their willingness. If you're a do-it-yourself guy, there is an alternative.
You can simply swap the ECU circuit boards between old and replacement modulators. The ECU board is in the rectangular housing on the modulator held together by 4 tri-head security screws. The circuit board comes off w/ the housing and connects to the rest of the modulator with a connector. The coding lives in the ECU's non-volitile memory. In general, the modulators fail because of a mechanical fault, not an ECU fault - so in all liklihood, your original ECU is perfectly good.
The only difficulty is getting the appropriate bit/driver for the trihead security screws. Snap-On sells them for about $12 each or you can get an entire 33 piece set from Wholesale Tool ( http://www.wttool.com/product-exec/p...ty_Bit_Set_WT_
) for about $7 (chinese made, but OK for occaisonal use).
I know this process works for the ABS II modules - don't know about others.