Many thanks, Allan, I got the iPhone to work again WITH the settings and data of the 3rd party apps.
I did find a Time Machine backup of JUL09 in the iPhone Backup file (in ~/Library/Application Support/MobileSync/Backup/),
restored it through Time Machine
then Restored the iPhone in iTunes to its original setting
closed and reopened iTunes
connected the iPhone: it asked me if I wanted to restore from a previous backup
I confirmed and chose the Backup of the date that I had restored with time machine
That took a while
To my horror, after the restore, there were no 3rd party apps on the iPhone
went back to Applications on the left of iTunes, clicked on the Update of Apps (or some such words)
it updated all of the apps
then synced them to the iPhone and
Presto, the iphone was in the state of JUL09.
Muchos gracias for all your advice and patience.
Cheers,
Veit
P.S. Here is the URL to the Apple note on making backups of the iPhone:
http://support.apple.com/kb/HT1766?viewlocale=en_US