Tricky application (backing up roaming laptops), to which I don't yet have a good solution...
You could install cygwin (or cwrsync) and configure a script that runs on the laptops to connect to your SME and perform an rsync backup.
You could use WinSCP to "synchronize" your laptops with a location on the SME server.
I think that BackupPC allows laptop backups -- but seemed very tricky to setup when I tried a year or two ago...
You could use VPNs to connect to your SME, mount a share, and backup to that.
To answer your actual question, though, I suspect you need to include the username or ibay name in the URL when creating your "Network Place":
https://user@sme.server.com/url or
https://ibay@sme.server.com/ibayOr, if you open the webdav share with Internet Explorer there may be a way to convert that into an Explorer window, which you could then add to "my network places" (I thought I'd seen instructions on this once, but I can't figure out how to do it looking at my IE 7 right now...)