I haven't found a solution to this yet:
I have 2 network driver established. They reconnect during reboots and are accessible fine.
For some reason they stopped being visible in explorer until I explicitly go to them by enteing the letter in the address bar. Then one or both with show up (usually just the one I put in)
I also have an internet webdav drive that also does not show up until i put it's letter in the address bar.
If I use applications to access the letters, they show up ok in that application's file open/save box.