I'm using a Genius PenSketch 9x12 with Inkscape 0.47. I run Windows 7 on my laptop and Windows XP on my desktop, both with the same problem. Inkscape picks up my tablet with no troubles (visible in the preferences), but it seems to have trouble setting the cursor position. When I draw with, e.g. the pen, it only picks up the Y coordinates (up and down). The X coordinates do change but I can only move the pen about an inch from the left side. It would seem that the ratio/scale of the X coordinates do not match the tablet. The ruler indicates correct movement on the Y axis, but no more than an inch of movement on the X. I use other graphics programs such as Corel Painter with no problems, and I have used this tablet with Inkscape version 0.46 with no trouble.
I have also compared the bug with version 0.46. The tablet works fine in 0.46 (in terms of the X and Y coordinates) but is unable to pick up the pressure sensitivity of the pen. In 0.47, which the X coordinates are clearly incorrect, the pressure is accurately picked up, so there might be something here that is causing the trouble.