I have an N900 with a no longer functioning GSM module. No amount of flashing I did was able to fix it, if that is the case with yours, you will likely get an error while the flasher is flashing the CMT, I also get that error message shown in your screenshot once during boot, and a second time when it has finished booting, also the built-in GPS no longer works and I believe it stopped working the same time the GSM module did.