[CentOS] Traffic shaping problem

Hi all,

I tried last week to do traffic shaping on a production system,
object of the exercise was simply to throttle the outgoing traffic.

tc qdisc add dev eth4 root tbf rate 300mbit burst 300kb latency 50ms

But the server became rather instable, crashing repeatedly without
anything in the logs.

Can anybody spot glaring mistakes in the tc command above,
or tell me what I should have done instead?

with kind regards,
  Bent Terp