error 1327 installing with system folder on mapped

I just installed Vista Beta 2, and I'm having some trouble with it.
Since WinXP, I've kept a few folders (My Documents, My Pictures, My Music, etc.) on a mapped drive. This allows me to leave my stuff on my server which is on 24/7 and accessible at all time.
But every modern program (let's say, Office 2007 Beta, or Doom3) I try to install gives me that error, 1327 ( http://support.installshield.com/kb/view.asp?articleid=q107033 ). Here's what I think the problem is:
The drive (M: in my case) is mounted with my user. When I try to install, it elevate to adminstrator privileges. But in doing so, it stops seeing the mapped network drive. So when it checks to see if the Documents folder is really there, it can't find it and so stops with an error.
Am I seeing things right? And if that is indeed the problem, how could I fix it?
Thanks