OK, if you wish to run both NX 4 (or any older lisenses) and NX 5 on the same system, you will need TWO license sheets and you will need to install and run TWO separate license servers.
One server will be installed using the license server software from the NX 4 kit, using your NX 4 license sheet and the default name will be 'UGS NX 4.0 FLEXlm' and it will be assigned, unless you change it, system tcp-port 27000.
Now for NX 5, you will need to install a second license server, this time using the NX 5 kit and using an NX 5 license sheet. This server will be given the default name 'UGSLicensing' and will no longer be unique to NX since it will be also used to control ALL other Siemens PLM Software products, such as TeamCenter, Ideas, Technamatix, etc., and it will use, by default tcp-port 28000.
Note that these two servers can run side-by-side without any complications or conflicts, but you will need to get from us a two different license sheets and you will have to work out some sort of arrangement with our people so that you are not in effect getting double the number of seats of software. I'm not aware of the exact details as to how we're handling this, you'll have to take that up with your Siemens sales rep and/or installation coordiantor.
John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
Cypress, CA