Okay, I managed to get hold of a Wacom Bamboo tablet today.
The issue only seemed to happen on Windows 8, and was seemingly caused by us telling the TSF run info that it had a length much greater than the maximum buffer size it told us was available - I’m guessing this caused TSF to overrun an internal buffer.
Should be fixed by 23cb8cbc5b90b684f65edd2c0a21a731d219fd56