You did not provide any environmental info (Windows version/Edition, etc.) but assuming the server name and so forth are correct then the issue is almost certainly with file and share security. Windows 2008 and 2008R2 "enhanced" security to the point that it can drive one to drinking.

I don't understand it well but even though my login has Local Administrator rights on both servers (source and target) I often find that I have to log on to the source server and set up either the Share or File permissions for my specific login. Sometimes I have to set the permissions at multiple folder levels and even on the individual files.

HTH, YMMV

Good luck.