Following this thread
Login to phpmyadmin as root, go to the dbispconfig database and there to the table "server". In this table there is a record for your server which has a column 'updated'. Increase the value of the updated field by 1 (updated = updated + 1) to skip the failed job.
I was able to clear the job queue.
Now I observe that job queue for deletion works find, but while inserting webdomain etc. it hangs, it creates folders in /var/www/clients/ but symlinks for webdomain in var/www and var/www/clients are not created and job queue constantly shows pending.
I also get this error occasionally in the cron file
chattr: No such file or directory while trying to stat /var/www/clients/client70/web111
I am completely stuck and need help to overcome this problem.