I had to go from 3.1 to 3.7 then to 4.1.2
The reason is that I did not want to lose any backups during the upgrade.
The 3.1 client is not supported under 4.1 server but is on 3.7  I brought
server up to 3.7 upgraded all clients to 4.1.2 (latest available at the
time) then upgraded to 4.1 server.
Watch your Netware servers because I lost long name support on 4 servers.
One crashed during upgrade (not related) & had to go back 2 weeks to restore
with long file names.  My suggestion is to use 4.1.2.14 According to Tivoli
the memory leak is fixed (you don't need to use cron to start scheduler).
If you are supporting long file names on your Netware servers make sure the
MEMORYEFFICIENTBACKUP option is set to YES in dsm.opt