Willaw,
As I mentioned in another post (Diagnostic mode) I also had this disabled navigation button.
This did fix by itself, even though it took days. Just make sure you have a working DVD in the system.

Recently I bought the new 2008/2009 disc and initially got the same side effect.
It says upgrading the software would take about 15 minutes. System did reboot each 20 seconds. I let it doing this for an hour until I lost faith and patience and restarted the car. Then I lost my navigation button again. But this time I did nothing forbidden, no fiddling with secret menus (or am I not allowed to restart my car?)

I just wanted to call my dealer, when suddenly, after a 1 hour city ride, the nav button came back.

I also can see that I have a new software now, since this stupid "I Agree"-screen now contains a web address which wasn't there before.

maybe you have to go through some 360 turning circle to calibrate the system  Former Mod/Member, with the most post & Chicken George Arch nemesis

Has anyone updated there sat nav and had any problems like this.

I to have bought the new updated discs for the sat nav, I have put the UK one in and the screen displayed a message saying that a Software update was required and not to proceed any further with the installation So I thought ok I will have to get that done at the dealer, so I put the old disc back in and now I have no Sat Nav, all I get with the old disc is the usual start up screen with the two buttons saying Navigation or Settings, Settings works ok but Navigation just beeps and does nothing and the screen keeps going off and coming back on about every 30 seconds.

Has anyone else had this, solved this or like me wished there had not touched it.  p****d off with a Digital Keyboard Warrior