Windows 7 C: drive permissions - file copy problem

So with Windows 7, it appears that even a local administrator user account can't copy data to the root of the C: drive...without giving explicit "run" rights as an administrator (when I try to copy something to the root C: I get a window that says "denied" and that I need to provide administrator permissions to copy this file).   However, I have a few mapped network drives from our file server, and if I try to copy a word document (for example) to my root C: from a mapped network drive, I gives me the following error:

Location is not available
P:\ refers to a location that is unavailable.  It could be on a hard drive on this computer, or on a network.  Check to make sure that the disk is properly inserted, or that you are connected to the Internet or your network, and then try again...

But, I am connected properly...and the network drive is still there.  I can copy files from the network drive to my desktop (for example) without any problem.  Why is this happening and how do I "fix" it?