Ok so this is not a question why there is this message but how to prevent this. My phone is at Nokia care at the moment and when i have it back and i should have a problem again with PR1.1 or 1.2, i dont want to bring it back to Nokia care again. Is there some way to modify the firmware so i can put on it whatever i want? Or is this not legal? I dont know who came up with this idea at Nokia but in my opinion, it only creates problems. My mobile is now 1 week away and no one knows how long it will take (one guy said one week, the other said "i dont know, maybe 4 weeks").

The security framework prevents firmware downgrades. No known workarounds.

My personal (possibly risky, unsupported and voiding warrany) tactic for flashing my N9 when I brick it is to use Navifirm firmwares only.

Find a "valid" Navifirm firmwareversion and use the same files (root-fs and MMC) every time you needs to reflash the device.

It seems that the definition of "downgrade" is some kind of timestamp in the firmware file. Possibly the builddate of the firmware. I "think" that the name of the firmware does not have anything to do with "upgrade" or "downgrade", it is just the timestamp.

Same timestamp or newer is ok to flash so if avoiding the official OTA upgrade with possible newer timestamp than in Navifirm makes it possible to restore the phone. I have noticed that it is easy to brick the phone while playing with apt-get xx.

The timestamp is reported by the flasher when failing due to downgrade as:
Downgrade disallowed (1324298652)
The numbers seems to be "Unix-time" so in a linux pc one can take that figures to get the timestamp:
a@gulan ~ $ date -d @1324298652
Mon Dec 19 13:44:12 CET 2011

errrm sorry but i dont know any other way so i already did that and it didnt work. Even nokia care in Germany couldnt do it (they also said they have this downgrade disallowed problem) so it was sent to Nokia

I had the same problem after a joyful first week using the device, in my case the update PR1.1 I got OTA was timestamped 3rd of January, and in navifirm I could only find older images, getting "downgrade disallowed (3rd of January timestamp)".

I was advised to wait for PR1.2 to appear in navifirm, it was said to be available at the end of February. Apparently sooner than Nokia Care (the 4 weeks you quoted). I can let you know if it works as soon as PR1.2 is online.

In my case I broke the distribution with apt-get autoremove, a fairly common command in debian based linuxes. What I can't understand is why don't they release the same timestamped images that you get OTA, so it would allow us to restore it in 15 minutes.

The idea is to use only images from navifirm, never upgrade OTA again. Unfortunately now you are in a dead end, as the images in navifirm are older than what you got OTA. First you have to recover to a working phone state, you have to either wait for navifirm PR1.2 and flash it yourself, or take it to nokia care (I imagine they are going to flash a PR1.0 or 1.1 image). From then on, just flash PR1.2, PR1.3, etc. from navifirm (and resist the temptation to upgrade OTA with that recurrent icon advertising newer distributions). If you happen to upgrade OTA to the last distribution available, let's call it PR1.5, and you break it, the only option would be Nokia Care, if they don't release navifirm images timestamped accordingly, what in my opinion is very disappointing.

well in the end, it took 9 days for my new device to show up so you would still be faster but i cannot garuantee that