Using DRTCP to fix your MaxMTUHopefully you can get connected long enough to download this file. Maybe download it from another workstation and copy to a floppy disk or USB drive.
Run this program and change the MaxMTU from 1500 to 1024 (if blank, put in 1024). Under the Adapter Settings you'll have a list of the different network cards. Laptops will usually have two, one for using a wired connection and another for wireless. Just choose them all and fix their MaxMTU size.
Also make sure your adminstator has not blocked ICMP packets at the firewall or from your workstation. This causes the MTU Path Discovery to fail.