.net - Using A FileStream On A Network When The Network Drops?

I am writing some code as part of a framework for opening a file.The file is of custom type and should not be opened by more than one instance of my application. To stop multiple file opening I use a filestream to create a lock file and then keep said filestream open. This seems to work in preventing another instance of my application from opening the file ( as it will fail in recreating the lock stream in the files open code ) but if the file is on a network share and the network drops then the original application also can not access the file any more.The code to get the lock stream is as follows:

Try
' We need to keep this stream alive to prevent other applications gaining access to the lock
mLockStream = New FileStream(mLockPath, FileMode.CreateNew, FileAccess.Write, FileShare.None)[code]....

In this I create the lock stream the first time round and then if another application tries to create it, it throws an exception and stops them from getting any further. This is kind of how it needs to work, unfortunately as I said, if this is done across a network and then the network connection is dropped for some reason then I can not delete the lock stream as I get an IOException telling me a process cannot access the file as it is open in another process ( which shouldn't be happening I don't think).