I had the same issue. If the file c:\Windows\System32\net.exe permissions are not set with local user group "User" with Read, Read and Execute, it will give you the following errors:
10/1/10 1:51:46 PM INFO Scan started
10/1/10 1:51:46 PM INFO Started scanning Share: \\xxxxxxxx\xxxxxxx\
10/1/10 1:51:46 PM WARNING Failed to read \\xxxxxxxxx\xxxxxx\; error: Unknown Error -- Access is denied.
10/1/10 1:51:46 PM WARNING Failed to complete Share: \\xxxxxx\xxxxxxx\; error: Unknown Error -- Access is denied.
10/1/10 1:51:46 PM INFO Scan finished
Once I added the Local User group with those permissions it was able to remotely log in and scan.