If the trackball is off 45 degrees, you could not fix this with software. The trackball basically has 2 small wheels that sense where the ball is rolling - an "up/down wheel" and a "right/left". When the trackball is installed correctly, the only wheel moving when you roll the ball up is the "up/down" wheel in the up direction, roll it down - the "up/down" wheel in the down, roll it left the "left/right" wheel in the left direction, right "left/right" in the right direction. When you roll it diagonally then both wheels are moving - like if you roll it diagonally in a north-east direction, the up/down wheel is moving up and the left/right wheel is moving right. If you installed it 90 degrees of like JD said you could just reverse the wheels (up/down would be left/right, left/right would be up/down). If it is off by 45 degrees as it is here, you can't fix it because when you roll up both the up/down and left/right wheels are moving, so the software can only do a diagonal line with that no matter how you tweak it.
As for mounting it correctly, it isn't really a diamod shape, the up/down and right/left sides are actually at right angles of each other (with the corner cut out, so it appears to be a diamond shape). The right angled sides need to be installed at that right angle, the top being parallel with one edge of the CP and the side parallel with the side of the CP. Not sure about the Ultimarc, but most have an arrow imprinted on it which indicates which side is the "up/down" side. This diargram is for mine, the Happ - hard to see with all the lines, but if you look closely you can see it is actually shaped like a square with the corners cut out.
