The other morning I recieved a notification about a "device update", which basically is an update for the same version as I already have flashed. Guess there's some difference in the versions.

However, if I try to update it just says "connection to the application provider was lost. try again later". And the notification stays there.

I fear it will even break my device if I install it as I have inception and stuff installed and modified sys-ui so I made complete backups just in case.

As it isn't able to update the notification won't go away and there's no way to delete that notification as far as I know.

Is there some magic trick I can do to make it go away or is it only a reflash to another version that will help?

The update says: 40.2012.21-3.232.05.2

I have: 40.2012.21-3.232.05.2_PR_232 (according to about page)

Here is something you can try if nothing else has worked:
- go to /var/lib/dpkg/
- take a backup copy of the ststus file: cp status status.BAK
- edit that file: vi status
- search for a line beginning with "Package: mp-harmattan" (I think in your case will be mp-harmattan-232-pr)
- six lines below there is one like: "Version: 40.2012.21-3.232.05.2"
- edit that line so that version is e.g. 41.2012.21-3.232.05.2
- save file and exit from editor
- check for package upgrades again

What should happen is that now the upgrade system believes your device version is 41.something, and what is available is 40.something, a lower number so there is no upgrade for you.
And it should make the green notification disappear.
Should be there any further official upgrade it will very likely have a version number bigger than 41 so you won't lose any real notification. Just in case...

I briefly tested with my device, by bringing first the 'faked' level down, checking upgrades, which has shown the 40.something available on Nokia servers.
Then I raised again the level to the original and rechecked for available upgrades and the notification has disappeared.

It would be also a good idea before you do that to double-check why you get that notification.
Just run "apt-get policy mp-harmattan-232-pr" and compare Installed: and Candidate: fields.

WOW!

That actually worked. I bow to your supreme knowledge. Amazing! The notification went away as soon as I checked for new packages after I had done what you explained so well.

Thanks a lot!

Sorry missed that part I was too eager to do the other stuff. However the update was only 1.7mb it said so it wasn't much to be updated.

It was Nokia Link update?

It fixes connection for other people and breaks it for some people.
So if your 3g and stuff works it wasnt needed in your country.

Don't think so I got that update right after I flashed the firmware like a week ago. I have had the 3G issue before (where it often loses data connection and needs reboot) on my first N9 on the same carrier as I have now so I hope it will be fixed. I didn't only lose data I lost everyting. Calls/sms too over regular network. Don't have a simcard in my phone for about a week longer it's only on WIFI at the moment. Missing simcard tray.