I get a lot of "late collisions", what are those?

Late collisions are usually caused by an ethernet switch and
a ethernet host disagreeing on whether to run full-duplex or
half-duplex.

When a Sun complains about "late collisions", it runs in half-duplex
mode but the switch it is connected to thinks it should run in
full-duplex mode.

In full-duplex mode, collisions cannot occur.