This sounds like a nasty Tablet PC bug which (fortunately) I have not yet experienced. I hope someone from Microsoft is all over this because, as the screenshot above shows, Tablet PC Talk has confirmed it.

So figuratively speaking, the computer fills up with ink - until it can take no more. Tabtip.exe is quite an important application - it’s the built-in ink digitizer responsible for handwriting recognition. Without it, you must buy and install a third-party recognition software, or plug in a keyboard.