I doubt it's a multiple core issue, I run Ryzom across all 8 cpus (Win 7 pro 2x quad core processors) with noticeable improvement and no crashing other than the random Zora crash that's been around since 2004. I've even run multiple clients across all 8 cpus and experienced no issues. This has been the case on 7 different computers, all running Win 7 Pro, 3 desktop and 4 laptop. Having said that Win 7 Ent may, of course, have other issues that are causing the lock-up.
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Eldest, Order of the White Lotus