I've got a really weird situation with one workstation on my network.
Topology:
Comcast Business class modem/router -> D-Link gigabit switch (192.168.42.0/24) -> Linksys EA6500 router/AP (192.168.1.0/24) DHCP/DNS handled by Win2k12 server
When I connect this Windows 7 Pro workstation directly to the Comcast router, Outlook goes berserk, constantly connecting and disconnecting from the Exchange server and yielding all sorts of errors about being unable to access other email accounts. Internet pages completely fail to load. The computer is sluggish and unusable. But all of these problems are intermittent.
When I connect the same workstation to the switch (still pulling from the *.42.0 pool) I have the same issues.
But when I connect the workstation to the AP (wired), it behaves itself...no problems.
Connectivity across all other workstations and wireless devices is fine.
What on earth could be causing a situation like this? I'm more than a bit stumped.