It depends on how your client is set up as to how it decides it's node-type (and hence what hierarchy it uses to resolve names).
I'm going from memory here, but...
If you specifically state DHCP option 46, it'll choose this, but if you don't then it looks at whether you have things like WINS and DNS servers configured, and whether you have a dynamic or static IP address.
A node-type of 0x8 is the best choice IMHO, which gives you name resolution via DNS then WINS then broadcast then hosts then lmhosts, but others are possible.
WINS is deprecated as of Windows 2000 onwards anyway, so you really shouldn't be using that any more, and should remove any WINS servers from your network (and the associated settings in your TCP/IP stack).
Just done a google, and you can manually set the node type in the registry, which might solve your specific issue (not that i'd advocate that normally):
Network Uptime: Troubleshooting WINS Broadcasts