将托管线程上的模拟令牌传递给非托管线程

I have a case where a VB.Net winforms app needs to play WMV files from across the network. The user running the app cannot be given direct access to the network share. Through impersonation, I can see that the files exist (without impersonation, File.Exists returns false for the files on the network share). When I then try to load the file into a Windows Media Player control, the control just remains black. I have deduced that when the Windows Media Player control is loaded into memory, it is running on a separate unmanaged thread than the .Net managed thread. Is there any way to pass that security token from the managed thread to the unmanaged thread? Am I missing something completely?I have a case where a VB.Net winforms app needs