I used a UAD-1 card with W7, X1d 32-bit for a year or so. Maybe a bit less.
Anyhow, it was never the cause of a crash. Steven Slate on the other hand...
But you have to NOT upgrade past 6.1 or something like that. They have the info on the UAD website, but at a certain point they simply stopped including UAD-1 in the new UAD-2 software updates.
Also, I'm not sure exactly but I do know that others had issue with UAD in general with X2 and a certain version number of UAD-2 software. You probably do not need to worry since your software will need to be older to use the card.