Svchost.exe showing very high usage

Yesterday, Norton notified me that svchost.exe is using about 248MB of RAM and sometimes '74% of at least one CPU' I know svchost.exe is a very legitimate process and File Insight gives it a Reliable rating, but still is 248MB of RAM and 74% of CPU usage normal? A full scan found nothing though and even today I am being notified of high usage by svchost.exe...