Application installation over network

I have an application that installs files locally and is then pointed to a
network share for the location of the database. My vista business box maps
the share without any problems, however when I run through the installation,
the installer does not see any of my network shares as a valid drive letter.
None of the network shares I have mapped appear with the other drive letters
in the dropdown menu. This same app ran fine in XP pro on the same server.
I am not sure if Vista is treating my mapped drives differently or what. Any
help is greatly appreciated.