K, thanks for your hint, I had searched for mp-fremantle-205-pr but found nothing. Searching for mp-fremantle I found they talked about mp-fremantle-generic-pr in the overclocking thread.

This is what I did:
- Restored original state (obex 0.18)
- Installed this mp-fremantle-generic-pr hoping that this would also install mp-fremantle-205-pr with this command:
apt-get install --reinstall mp-fremantle-generic-pr
(This also installed me some other packages: maemo-optify-runonce, rtcom-accounts-plugin-facebook, modest-home-applet, libqt4-multimedia, rtcom-skype-emoticons-theme, rtcom-accounts-voip-support, cherry, no idea why and hope this doesn´t cause any trouble in the future or with other installed apps, However, mp-fremantle-205-pr was NOT included... )
- Installed your .debs (libopenobex2 and obexd2)

So far everything looks fine and also no false update notification, but, I have still no idea how to get mp-fremantle-205-pr reinstalled :-(