I just purchased a 871 (non-wireless) and during the intial setup I couldnt get the 3 port up. All out of options I created a Vlan with all the ports inside, gave it an ip address and brought it up.
when I connected a straight through cable from the router to the PC the port wouldnt come up, but when I connected a crossover, the port came up.
Why would it not come up on a straight through.
A router and a PC would be peer devices (i.e., both are made to plug into a switch), or you could say they are both DTE devices.
As such, the most appropriate cable would be a crossover cable.
That aside, at least some of the switch modules are auto MDI/MDI-X and should adapt. If the PC NIC is old enough, it may not cooperate with speed/duplex auto-discovery.
There are some other factors, sometimes just hard coding one side screws up discovery for the other side.
What version of IOS are you running?
Have you tried a scratch install?
Are you sure that you are using a good straight through patch cable? The 871 router supports MDIX auto which means that the switch port will automatically cross over the pairs in hardware.