No matter how much you test in a lab and read on the forums, always be
prepared for the worst!

On Friday night I applied SP5 to two of my NetWare 6.5 sp3 servers.

Here's what happened:

Support pack installation hung at 98% (iManager). Server was locked up
solid. Rebooted server. Java environment totally broken - unable to start
GUI, unable to rollout of the SP, everything was a mess.
Found out how to unpack the java files from the support pack manually at
the server console, then rebooted server. Java now working, managed to
rollout of support pack installation, rebooted server.
Uninstalled iManager, rebooted server.
Installed support pack - this time it worked.
Installed iManager from SP5 overlay CD, rebooted server.
Installed other post SP5 patches.

Now my 2 servers seem to be happy.

My 2 hours of downtime stretched to 10 hours, but alls well that ends
well, except for the few more grey hairs that have appeared :->