DNS intermittently fails to resolve

I’m having a weird DNS issue in which the DNS intermittently fails to resolve for one machine in a workgroup of about twenty. The user loses the ability to browse the Web, but can access IP addresses normally.

No other users have indicated a problem. The DNS on the machine in question has been flushed. For grins, the switch that the machine is connected to has been reset.

Any thoughts? Unfortunately, I haven’t been able to reproduce the issue on another machine and the issue comes and goes on the affected machine as well.