DHCP Users Lose Correct DNS Address

My users that use DHCP to get a network address are sometimes losing connectivity due to their DNS address being changed. The DNS is run on the domain controller which is Windows 2003.

When they first obtain their lease, they show the proper address (192.168.50.5). They’ll be working fine, then after some time they magically lose the proper DNS address and it changes to 192.168.15.1, though the rest of their information is fine and they can still ping via IP. Renewing the lease fixes the problem and they can go about their business.

I’ve never experienced this before and don’t really know where to start looking. Any help is greatly appreciated!