Cant save network locations in favorites. They keep disappearing!

I save a bunch of network locations I use each day under my Favorites in Finder, yet from time to time, more often than not, Favorites will not save them and they disappear from my list! Its really becoming frustrating! Does anyone have a solution?

The locations are on a networked computer (Windows) that is all hard wired. Its on a fixed or static IP so doesn't change.

I drag the folder location over to Favorites. I believe when I take my computer home or disconnect form the network I lose the favorites folders and have to put them back from time to time. Doesn't do it all the time just randomly. Can anyone help explain?