Collection On Network Share - Why does Zune software periodically clear out library?

Here's my config : 150GB music stored on Windows Home Server Laptop PC with M: drive mapped to WHS music share Zune Software on Laptop PC monitors M: drive Problem Setup : I often use my laptop when I'm away from my WHS, for example at work or when traveling. In this case I'll listen to music on my Zune device. Sometimes I'll open the Zune software because I want to download something from marketplace or update a podcast. In both these cases, Zune is set to download the files to my laptop's HD (usual C: drive location). Issue : The Zune software will suddenly decide that I must have deleted all my music and starts clearing out my library. When I reconnect to the WHS it starts adding it all back again. It also needs to resync tracks back to my Zune. With a library of 25,000+ tracks this is a complete pain. It seems like it's caused by the M: drive not being available. Does anyone know what would cause the Zune software to "notice" this and decide clearing the library is the best course of action? Is it amount of time after I start the software? Number of times I start it without the network drive attached? At least if I know the trigger I can avoid it!

You are set to smart sync apparently.  In that case, the software is doing precisely what it is designed to do...monitor the M: drive (in your case) for changes to your collection, and synchronize those to your zune device.  If you must open the software when the monitored folder is not available, and you want it not to remove that material from the zune, you will have to switch to manual sync.  In this case, you will have to manually sync anything to the zune.  And, your collection will disappear and reappear as you open the software without or with the M: drive present.