It absolutely can be caused by memory. But other things can do it too, inadequate PSUs for one and a "bad" driver iteration for another.

The best way to prevent / check for memory issues is to Memtest each new memory stick on its own for a few hours, then run another pass or two with all installed. It's a pain to spend a day doing this when you want to install it and go, but it catches the majority of memory issues, and the alternative can be phantom crashes driving you nuts if one of the sticks was bad or if the settings in the BIOS don't work for the installed set.

Vista does do some things differently, so what you're thinking isn't too far-fetched. I think the main effect would be that it's a little more finicky about less-than-stable states that XP will continue unaware of. If you take the time to do rigorous checks of a new part / system, it should eliminate it in many cases.