I got my SMP 6.0 license, and I cannot upgrade the firmware on the equipment I manage. Sofaware says that I now require an 'UPD' license according to a licensing document. This UPD license is nowhere to be found on any price lists, and in the meantime there's no firmware upgrade.
Anyone has run into this issue?

I do not know if you are stil interested in an answer, if yes, you are correct, you need a license SMP-FIRM-UPD-5USR. you could take a look at this page for example to see prices.:

http://www.softwareforless.com/mfg.asp?MFG_DESC=CHECK%2...NT%20SOFTWARE%20TECH