Low Ethernet Link Speed on E6510

I have a wired network with a router (which also acts as the network's DHCP server).

I just plugged my new Dell Latitude E6510 into the network and am having troubles. I can connect to the Internet only if I manually set the adapter's link speed to 10 Mbps with full duplex. If I set the adapter to Auto Configure the link speed, or if I set the link speed to 100 Mbps, the connection fails, and diagnostics tell me that no DHCP server is available. If I set the link speed back to 10 Mbps, without making any other configuration changes, the DHCP server becomes available and I can connect (slowly).

Other machines on the network, including a Dell Latitude D620, have no problems connecting to the same network at 100 Mbps using auto configured link speeds. I went to Intel's Web site and downloaded the latest driver for the network controller, but I'm still not having any luck.

Any suggestions on getting me connected at 100 Mbps?