OK, I did something else, I saw a .qf file in the n900 phone's flash memory. I made a copy of that, and renamed it to qf (without the dot in front, unhides the file) then I made a same copy of qf and put it into the sd card as well.

So there are 2 identical files named "qf", one on sd card and one in phone memory. The 2 qf files seem to apppear as 1 file in PC Suite mode, and the n900 is detected in PC Suite mode. I haven't tried uploading any maps yet. Still playing around.

P.S. I'm using Win 7 64-bit, nokia map loader version is 3.0.28.0.