TFTP Fail

environment:

Novell Netware 6.5 with Sp6
NDS version 10553.73
Novell eDirectory Version 8.7.3.9 SMP
Zenworks Imaging Server version 7.01

After upgrading to SP6 we get the following error when entering the
Zenworks Boot: TFTP Illegal operation and lot of useless characters.
At this point the name resolution fail.
The only solution is rebooting the server.

We want to patch 12 imaging server in other locations next week
- its urgent.

Any ideas?

Thanks.