Same is happening to me, so far its always my home world and always on exiting the planet.
Updated my radeon drivers to 8.8 and I thought that had fixed it, but no a few mins ago boom again.
What with the frustrating frequency of assualts on my home world i'm getting close this last time I came close to biting through my keyboard. grrr
O/S was recently updated to xp home sp3, sent the automated crash report to ms.