How to Update firmware to V 5 with Nokia Software Updater
I had to find my own solution cause Nokia Software Updater (from now on NSU) wouldn't let me download the latest firmware or re-flash the current one (see my post on Start Over the N80).
Specifically after a hard reset (more than just 7370) you need to re-flash the original firmware to get back the default applications that were in the Phone. The Nokia website offers all of them, but they are not updated (they can be older than what your previous firmware had), so this is quite misbecoming since you are trying to update not to get back the past !
So you go on with the NSU and try to re-flash the firmware, or seek for a new one. But the NSU seems not to find the new one, and doesn't offer you the chance to reinstall the old.
As far as I know the only way to workaround this HUGE problem with ease (i.e. not wasting life writing yourself an application for the matter) is to change the product code with the Nemesis Service Suite (NSS) .
For a product code able to trigger the NSU to download the latest firmware release 5.0719.0.2 you find reference in this thread  Also, the same codes that I tried (mention will follow) are either able to obtain the latest firmware and re-flash the same firmware with my test (actually my own) Nokia N80 IE.
The original retail country for my N80 was Germany. Using NSS I switched the product code to 0526966 and tried the update. All went well and I finally had the new V5 firmware. But that code was meant for scandinavian countries, and despite the owed english version it was missing my native language. So I tried this code tagged as "Euro Pearl Black" 0529381. The NSU program was smart enough to re-download only the parts needed and began working at 40% or so of the download process. Once flash was done I had again the usual West European languages: English, French, German, Italian, Spanish, Portuguese.
The latest firmware's software suite includes Adobe Reader, QuickOffice Viewer, WLan Wizard, WLan scanner, the Nokia Lifeblog and the Download app. All software you lose in case of a hard reset and the only way to put it back in the same way it was is to re-flash the firmware. That's why firmware upgrade/re-flash is so important to me.
I'd suggest you to take note about the codes and install right away the correct language. Find more references on this thread .
To complete the procedure and avoid contractual penalties I then went back to NSS and flashed back my N80 IE original product code.
Mission Accomplished !
Maybe it had been a bit easier if I found a post like this.
I Hope this could be of a help for those having firmware update problems with stuck product code.