I'd like to resurrect this thread, see if anybody else has similar problems (or fixes). Seems my accelerometer values have drifted over time. This is primarily a problem for me because my N900 often doesn't realise it's being held in portrait mode.

Laying flat, AccDisplay now tells me:

• X: 0.4
• Y: -0.05
• Z: -1.13

This means that for the N900 to think it's lying flat, I need to tip it at an angle along the bottom edge (the edge with the physical lock key and the VA jack) to between 35° and 40°.

It's the x-axis which has drifted the most since my last post. If I test the extremities, I see the following values:

• X: -0.59:1.46
• Y: -0.97:0.95
• Z: -1.13:0.9

The Y and Z axes are basically the same as before, excepting minor artifacts from my less-than-rigorous testing. The extremities on the X axis are much more severe.

So, does anybody know of any fixes?

I've tried battery out and power up 'fix', but it doesn't seem to work. But I'm also not sure why it would fix the issue in the first place, or what orientation the phone should be in when it boots if it does.