crash every 30 min to an hour.

[kiakaha]

Hmm that out of memory error usually occurs when you play Ryzom for a long time (there is an as yet unfixed memory leak left. ) When the memory usage goes to 1.5Gb it then crashes with this error.

I can't see why it'd happen with only 45 mins in game though.

Seeing as you have an NVidia card, perhaps you should put it to use OpenGL.