This bug is now fixed. A new version is available at http://www.maplorer.com/maplorer.html
The inversion concerned also north and south - it would be realy great if someone from Australia or New Zealand could test this!
Western (Americas, ...) and Southern coordinates (Australia) must be given as negative in the POS files.
Thanks again for reporting the problem.
However when following a track, I noticed that as I moved left and up screen, my track moved up and right. It also showed my present position wrong on startup, though the raw GPS position data was correct.
So I reversed the Longitude numbers (TR to BL) in the .ini file and everything worked fine. I live in the northeast US, and my Longitude numbers are negative, perhaps there is a simple "sign" mistake in your screen movement direction algorithm?