I have lost communication with my router. I cannot get to the login screen. My question is will unplugging the router and plugging it back in re-start the router and allow me to login? Will this re-set it to factory defaults?
Before doing anything I would have a look at the literature which came with the router (or download the full manual from 3com).
If this is a wireless router and the problem is wireless you will still be able to reach the user setup screens with an ethernet cable connected to if from the computer.
Once in you should be able to soft boot the router which may sort things out.
If it's not working by cable, the reset button is usually concealed behind a pinhole and there's a procedure for resetting to factory defaults (though usually just holding it down with power on will do the trick). It's a bit of a last resort because in addition to the LAN (local) settings the WAN (internet) settings may be wiped so you may need advice from your ISP on re-entering them.