You do have the LMHOSTS enabled, right?
Make sure the Lmhosts lookup is enabled by performing the following steps:
Click Start, point to Settings, and click Control Panel.
Double-click Networks, on the Protocols tab, and double-click TCP/IP Protocol.
On the WINS Address tab and click the Enable LMHOSTS Lookup to enable it.
NOTE: You need to restart your computer for this change to take effect.
