PSEXEC tries to connect to the Admin$ share of the remote computer, in order to copy on the remote machine the PSEXecSVC.exe, which is the binary of the Service that will run remotely.
If using a domain admin account you are not able to perform a network type logon like this one on the remote machine it is probably because the Admin$ share has been disable via a policy/registry key.
Try by yourself running a cmd as that Domain Admin user and then from that CMD issuing a net use \ComputerName\Admin$. You should get the same error.
HTH
-mario