T41 wakes from suspend-to-ram on its own

[dakrk]

My T41 suddenly wakes up from suspend-to-ram on its own.

Sometimes it's only 25 seconds between suspend and wakeup, sometimes it sleeps up to half an hour (according to logs).

It's not wake-on-USB as all USB devices are powered off and unplugged.
It's not wake-on-LAN, as I don't use it and my router prevents anyone from waking laptop up from the internet.
It's not wake-on-low-battery as I verified that by unplugging the laptop from AC while it was suspended - it does not wake up.
What can be the reason? Is the laptop old enough to suffer from insomnia?

I'm using Linux, but I've never seen the issue before and I have been using Linux at T41 for several years without alike problems.

[jdhurst]

Do you have a wireless mouse that wakes it up? My Logitech will wake up my Vista machine unless I turn the mouse off. ... JDH

[dakrk]

No, the only wireless module I have is Wi-fi (ipw2200), as far as I know, it does not support wake-on-WLAN.

[sjthinkpader]

How about disabling the UltraNav?

[dakrk]

I've not noticed "wake on UltraNav" option in the BIOS Setup and I actually use touchpad.

The laptop wakes up when the lid is closed so ultranav should not be touched at the moment.

Why do you assume that UltraNav may be source of the problem?

[jdhurst]

I don't think the UltraNav would wake up the laptop with the lid closed. WiFi won't do it either (even when set to Max Performance). The only thing on my own latop is the wireless mouse.

The T41 suspends by a nub on the lid that closes (opens) a microswitch on the main cable assembly (in that area at least). I am aware of that because I knocked mine off when replacing a hinge, so the sleep function had to be looked after manually. One possibility in this regard is that the switch has become intermittent.