Windows XP seems to work better.. but the alternative is to boot Linux from a USB stick.. this avoids using windows at all.. I've pretty much only ever heard of flashing problems on windows..

Macs and Linux generally seem great..

If you have a 2Gig usb stick kicking about, you could try these instructions I put together..

http://discussions.europe.nokia.com/.../693460#M11588

That'll let you flash your phone by booting from the USB stick.. It's seriously easier than trying to fix windows issues, imho