Windows 7: Opening file on mapped drive problems...

I have five Windows 7 PC's networked together, two via Ethernet cables, and three via wireless to an Aximcom MR108-N router. Each PC has the same User Id and Password, and all belong to the same Workgroup. The network works most of the time, but that is not my issue. The router and all PCs are all fully patched to latest updates.

1. I use one of these PC's as the 'Master' PC because it contains an MS Access 2003 database file which is then accessed by each of the other four PC's.
2. I have set up a mapped drive back to this Master PC and this all works okay. Thus from each of the 'client' PC's I can open Windows Explorer and view the files on my mapped Z: drive.

My problem is that on each of these 'client' PC's I have a desktop shortcut to open MS Access and open the specific database file on the PC I have called the Master. Thus in my desktop shortcut properties form, the Target field on the Shortcut tab shows: "C\Program Files\Microsoft Office\Office11\MSACCESS.EXE" Z:\Data\Access\MyDatabase.mdb /x start_macro
The 'Start in:' field is: C:\Data\Access

When I first click on this desktop shortcut MS Access opens, then an error message pops up that it can't find the 'Z:\Data\Access\MyDatabase.mdb' file.

If I stay within MS Access, and try to open the file on the mapped drive manually - via clicking the [My Computer] button (within Access), then double-click on the Z: or mapped drive list entry, I get a small delay, then the list of files on that mapped drive appear. If I then cancel everything, and close MS Access, and try to start the desktop shortcut again, it all works perfectly!

Why do I have to use the File Open utility within MS Access to see the file I want to open, when I can already see it in the Windows Explorer mapped drive entry?

Why can't the file be opened the FIRST time from my desktop shortcut?

Is it a Windows permission issue, or what do I have to do to enable this file to be opened as soon as Windows has successfully mapped the drive?

I appreciate your help and answers.

...MPD