Hi,
I've reflashed the IM-Me using GoodFET. It's pretty easy. I'm using Linux, but it may also be possible from Windows.
I have a GoodFET31. It wasn't too hard to assemble, but if you haven't tried surface mount soldering before then you might want to read up on it first (use plenty of flux and get a fine tipped iron). Travis Goodspeed will send you a PCB for $5 (or nothing if you're a student).
The IM-Me chip is a CC1110, which is an 8051 based microcontroller. SDCC does support this, but MSPGCC is for MSP430 only.
The GoodFET supports MSP430 JTAG, but I haven't tried it out y