I recently upgraded an NME-CUE (Cisco Unity Express Enhanced Network Module) from version 3.2.1 to 8.6.7. This module was moving from a 3845 router (running CUCME 7.1) to a 3945 router (running CUCME 10.5), so these versions match the compatibility matrix. On the whole, this went fairly smoothly, but there are a couple of issues to be aware of.
In brief, there were 4 main steps:
- Backup the current configuration and data.
 - Download and install the upgrade package.
 - Migrate licences to CSL.
 - Sort out the Message Waiting Indicator (MWI).