I have installed LN8.5.1 clients on both Vista and XP PCs. On 2 out of 20 PCs LN crashes leaving nds.exe error as an event.This occurs only onto those two PCs 1 or 2 times per day.
I had similar issues. I upgraded the users’ mailboxes who have crashing problem and seems to fix the issue. Also check if their mailbox is nearing their quota limit as this could cause the crash as well. Good luck.