Hello,
after all I solved this myself and want to share the solution.
First I did a snapshot of the whole machine, just in case something go completely wrong (thx to VMWare in that case!) ;o)
I did a backup of all configuration settings, like DomainID and such things via the SEPM Console (Server Private Key Backup)
Then I backed up the SEPM database with all the policy rulesets and client information via the Startmenu entry.
I de-installed the SEPM completely and did a reboot.
After that, I installed the newest version of SEPM and did an import of the settings via the Server Private Key Backup.
Log in with the default admin.
Logged out again and did an import of the database backup.
That´s all and now, the SEPM run fine! ;o)
BR,
Gil