Ah... yet another example of the many contributions made by qwerty12 to this community.

I have been using jacekowski's modified FMTX binary since Faheem turned us on to it last month

Here are some hopefully helpful hints that may lead to a more positive outcome:

1. Make sure FMTX is not enabled on your N900 before proceeding.

2. Remove and uninstall FM Boost, FMTX widget, and any third party application that calls to or modifies the stock FMTX.
You wont need them anyway as the modified binary outputs at max power and ignores events like plugging in the charger that previously reduced power.

3. Before placing the modified FMTXD file in usr/sbin, rename the one found there to preserve it in case you encounter a problem. Remember this new name and you can switch back using a rooted command line if all turns to crap.

4. If you do not need to use a frequency outside the ones provided by Nokia then install qwerty12's modified .so file using the DEB or source found >>HERE<< and all should work.