VPN Share error 2221

We are migrating from SBS 2008 to a new server 2012 and I'm setting up a VPN server, I can connect to the VPN without problems. But when trying to access a share I get the error User name cannot be found. But when I try to access the share based on IP address it works fine.

C:\Users\mats>net use J: \\192.168.10.2\Public
De opdracht is voltooid. (SUCCES)


C:\Users\mats>net use X: \\SERVER\Public
Systeemfout 2221.

Kan de gebruikersnaam niet vinden. (User name cannot be found)


C:\Users\mats>net use X: \\SERVER\Public PASSWORD# /u:DOMAIN\USERNAME
De opdracht is voltooid. (SUCCES)

Can someone point me in the right direction?