Somehow I find it hard to belive that it's OCPN that causes the crash in Vista.
Vista causes Vista to crash.... It's proven over and over again...
(As well known out there, Vista was a major step back for Microsoft when they released Vista - It should never have been released in public).
Have you done all updates to Vista (Windows Update - Select all available updates), if yes - Update all drivers for the motherboard and GFX card, if yes - update BIOS to the latest (not beta version).
My suggestion to all Vista owners - spend your money
on Windows7 and get rid of the Vistaheadache. It's faster and got 98% less bugs.
If you are not an advanced user, you will be good with 2GB- of RAM if you got a dedicated graphics-card inside the computer.
(hasta la Vista