And I agree with the Net Doctor---likely, I would guess there is a 3-Com switch in between and your Cisco is not negotiating the duplex, and thus you have a duplex mismatch. Another indicator is late collisions. Anyhow, 9 out of 10 times dribbles are caused from duplex mismatches, usually between unlike manufacturers.
/
tim@tim-laptop ~ $ sudo apt-get install windows
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Couldn't find package windows...Thank Goodness!