Problem as it is in subject
Nokia N 800 with OS 5.2008.43-7
1)Upon starting the system everything works just fine
2) If to connect to WiFi router - connection is established, After few seconds system stops to respond any activity tap/button press.
3) N800 goes to self reboot
4) Return to number 1)
Here is output
cat /proc/bootreason
32wd_to

Output of
cat /var/lib/dsme/stats/lifeguard_restarts
/usr/bin/hildon-input-method : 2
/usr/sbin/ke-recv : 2 *
/usr/bin/hildon-desktop : 1

I reflashed the unit couple of times. Initially Internet connection is established normal. After reinstalling my programs back to original state problem comes back with same symptoms.

How to avoid reboot upon establishing wifi connection?

Have you installed any new packages or updates recently? You could start by uninstalling those packages and see if the problem goes away. Or try installing packages one by one after reflashing to see what package is causing the problem. Could also be a corrupt config file that you are restoring after the flash.

If it is all clear about new packages, then what to do with "corrupt config file"?

Sounds like an old/weak battery. Could be internal dust shorting the antenna to the case.

Don't reinstall it.

But why would the wifi work fine to install all the apps and then fail everytime after that?

Just a sofrware problem. Reason was behind python packages installed from unproved repositories. These were restored from saved backup file upon restore. Solved by manual installation of all packages from Nokia approved repositories only. Most of the things are back to normal. Though versions are back to obsolete ones.