I would ask your server admin to tell you exactly what is going on.
Your error could easily be because you are running cron through the browser at the same time as cron is running in the background (very likely if a large site). The error you are seeing may be nothing to worry about.
Your error could easily be because you are running cron through the browser at the same time as cron is running in the background (very likely if a large site). The error you are seeing may be nothing to worry about.