The server is currently on a stop after we installed some more sites.
From host
All what I did was create pauses 2 sec between executing cronjobs for different sites. Issue is cron.php for almost each site run more than one minute so you have several simultaneously working cron.php processes for one site. It can be good idea to run these processes at least every 2 minutes to let previously started process finish it's work.
cron.php sometimes can work more then a minute if it tries to create trader's thumb while there's a problem with trader's host. Don't worry about that, check hardware load only.