I am experiencing some weird performance trying to scan from 1815dn via network.

4 Notebooks are connected to the printer via router. Alle of them having functional net-access. On one of them (Win7) scanning works fine.

Using Network-Scan on the other 3 computers (Win7, Vista)  I am not able to scan. When I try to add a new machine the 1815 is found with the correct ip-adress. When I insert ID and passwort and send information I am receiving an NetScan-Error: Unexpected error. Check your network connection.

Any Idea?