After trying new my.cnf, restarting mysql took to long (apparently due to some incompatible commands in the experimental config) , so I restored to my original my.cnf and restarts mysql successfully. But now I see that the site has gone off line. I tried the 'desparate' solution, i.e. issued:
UPDATE variable SET value = 's:1:"0";' WHERE name= 'site_offline'; DELETE FROM cache WHERE cid = 'variables';
but had no effect. Then I changed my database admin credentials. then, to possibly counter a corrupted table, I tried to repaire the database (MyISAM enginge) using
mysqlcheck -uroot -pPASS --auto-repair --optimize --databases MYDB
I also rebuilt the file permissions on the server.
No cure either.
I'd seen before that the site went offline on whim, but now this seems to become persistent. really appreciate your help to overcome this nasty problem.