If there is a problem accessing the server -- such as the server not being up, completely, or a damaged cable -- Windows will open a dialog stating this, prompting whether you want to restore the connection next time, with two buttons, Yes and No.
You should always press Enter
or click Yes! Responding "Yes" will keep the drive mappings in place for next time.
If you respond "No", Windows will discard the drive-mapping settings, and you will need to reassign them.
Click here for a "how-to" document on how to do
that. This is a PDF document and requires
Adobe Acrobat Reader to read it, which is free download, and you should have a copy on your
machine. If you don't, click here.
This means...
Doing anything else could leave work unsaved, corrupt databases, and all kinds of things we won't want to think about.