T42 won't go into standby or hibernate running on battery

[tomer]

this is really strange..
the monitor does turn off after the specified time on Windows power management or battery maximizer and on AC power everything works well (will go into standby and then hibernation just as configured) ... but not when running on battery. Fn-F4 works and also Fn-12 for hibernation, but not by itself.
I only use wireless network connection, but I don't think that's the issue.
what could this be?

UPDATE: I've done some testing and with the wireless networking (Fn-F5) turned off, it does go into standby .
is this how it's suppose to be?