I had the same problem with standby and hibernate. It was like the computer was hyperactive and couldn't just sit their and be energysaving.
It turned out that it was my eithernet connection. "Wake on LAN" was on.
If you have Cable/DLS connected through ethernet, do the following:
Start>Control Panel>System>Hardware*>Device Manager
(*Windows XP)
Then find your network adapter, then go to "Power Management" then unselect "Bring This Device Out Of Standby" and check "Let The Computer Turn Off This Device To Save Power"
(picture Below)
If that doesnt work, visit
www.trendmicro.com for a FREE virus/malware scan and REMOVAL