Hurray!
A big thank you to Paul, for sending the link on the document.
Short version;
I checked, and indeed, also on the backends the wrong folder was updated.
I uninstalled all extentions (backend and frontend).
I renamed the 6.5.7234.20 folder to 6.5.7234.20.OLD
I re-installed extentions and configured them.
resynced users
I tried, no icons and other options. DAMN!
Then recalled to empty IE-cache.
Voila, working environment.
Long version
On the backend exchangeservers, commandprompt in c:\program files\enterprise vault\owa\
type - cscript backend2003setup.wsf /remove
Add/remove programs, uninstall EV extentions
Remove Enterprise Vault folder from c:\program files
Renamed 6.5.7234.20 folder in c:\program files\exchsrv\exchweb folder
Install backend extentions
verified last control folder had extra folder (originals etc)
copied over evservers.txt file to c:\program files\enterprise vault\owa folder
start, programs, ev, configure backend extentions
On frontend exchange server
On the frontend exchangeserver, commandprompt in c:\program files\enterprise vault\owa\
type - cscript frontend2003setup.wsf /remove
Add/remove programs, uninstall EV extentions
Remove Enterprise Vault folder from c:\program files
Renamed 6.5.7234.20 folder in c:\program files\exchsrv\exchweb folder
Install frontend extentions
verified last control folder had extra folder (originals etc)
start, programs, ev, configure frontend extentions
On Vaultserver, in Vaultconsole, rightclick mailbox archiving task, properties, tab Synchronize, sync all users.
On client, empty IE-cache (start, programs, settings, controlpanel, IE-options, delete files and delete cookies)
Connect to frontend, login, voila.
I do have to enter username/password when opening Archive Explorer, but that is a minor (resolvable) issue
Thanks again.
Gertjan
Regards. Gertjan