I have a wireless router and an USB hard drive connected to it. Basic file access on the command line and Explorer works flawlessly after having set up some options on the router and mapping to some folders with

net use k: \\ROUTER\Folder1 /user:MYLAPTOP\Me password /persistent:yes
net use n: \\ROUTER\Folder2 /user:MYLAPTOP\Me password /persistent:yes

Robocopy (and using SyncToy for that matter) to a network drive however fails:

robocopy c:\Files k:\Backup /MIR /Z

gives

There is not enough space on the disk.
2010/01/05 09:52:11 ERROR 112 (0x00000070) Accessing Destination Directory N:\
Waiting 30 seconds...

The error message is misleading: there is plenty of space on the disk and the folders I'm copying are small. The router is an ASUS WL-500gp with a standard firmware. I'd appreciate if someone would be able to explain what is causing the problem and, if possible, how to fix it.