MSN idle... question please?

I know how msn idle works however something is happening that is confusing me. I've done multiple searches and can't find anything.

Scenerio: A person says, "I'm leaving my MSN on all day but won't be home." They leave and their msn doesn't go on IDLE at all for hours! Then MSN goes on idle (let's say) 4 hours later for a few minutes and then goes back to online. Then 3 hours later goes on idle again for 10 minutes and then back online. Then 2 hours later, goes on idle again for a few more minutes and back to online. They haven't been at home all day though... ? Does this happen? I know that idle goes off when the mouse is touched... but can it do what I've mentioned above if nobody is home (supposedly)?

This person lives ALONE so nothing else could have touched the mouse... and it wasn't idling while they were "out" but did spuratically throughout the day and hours in between.

Can someone explain?

I should correct myself... it wasn't on "constant" idle while they were out.... but would go on spuratically....

things like antivirus updated avtivate the computer. There also is a setting in Messenger to adjust the setting as to what timeframe before the "away" or "idle" will show

at top right of messenger click on .. "tools" and then.. "options".

Then under the "personal" tab you will see in the "my status" section.. "show me as away"

I think this is because the person has an optical mouse which moves slightly and brings the computer out of idle state. Just run a screensaver and see if it goes away when the mouse moves.