It seems that clamscan could never eat the chunks of mail sent to it, the server become 100% unresponsive and login took hours. clientsatisfaction became Zero, while you see the faxes arriving from customers cancelling the service and shouting "nOOb" all over.
I Backed up the old server after I managed to quickly stop services postfix and ispconfig_server as well as killed all processes to do with clamscan (It dint go away after even 30 minutes as predicted by Till)
It took me exactly 3H15 minutes from the moment I rebooted on the CD to re-install the server till up and running with "Perfect ubuntu 7.04", ISPConfig and Backup restored / user passwd/shadow/group/gshadow files fixed.
However only to be confronted with Exactly the same problem! At that stage Till's feedback arrived and I was confused, he told me to edit the scritpt /home/admispconfig/ispconfig/tools/clamav/bin/clamassassin and fix it to work with clamd/clamdscan. Well it took me to again untar the ISPConfig installation files and search through install_ispconfig directory and found the README for clamassassin, in there was an nice indication of what to do.
The lessons learned here is that it does not always help to use the "Microsoft Fix" i.e. - Reload, but rather seek the real issue, then start digging/googling.