>Did you confirm it? I'm using Win 7 64bit and Office 2010 64 bit - didn't see the problem. I just did another change, checked in WE - all is OK.
>
>What is the directory you're checking?

I didn't have time to check that from the .NET level. However, I installed Office 2010 SP1 this afternoon, and after the save, the document modified date was then updated. I also tried from a reboot before and that didn't change anything. So, it was at save time that the issue was not updating the last time stamp of the file on disk.