If you’ve had trouble like me trying to add a custom numbering scheme to Autodesk Vault Professional 2012, then you should take a look at this hotfix from Autodesk Support:
The Symptoms involved trying to create another Numbering Scheme, and after creating it, the thing would disappear. In my case, I had a test scheme in place, and was trying to add my corrected version. Autodesk says that it retains the original custom scheme.
You will have to restart everything in order for this to work. Additionally, read the readme. There are special instructions regarding the database. I didn’t read them and the fix didn’t work until I completed these instructions.