Sarge Automatically reboots

[Murali Krishnan Ganapathy <gmurali@cs.uchicago.edu>]

Hi List,
   Till last week, my Debian/Testing installation was working very well.
Last week I did an "apt-get upgrade". For the last few days, every time 
I boot, it goes all the way to the login prompt (disabled X for now), 
and even lets me login. After about 1-2 minutes of uptime, it just 
reboots. No Kernel Panic, no oops, no nothing. I also have a Windows 
installation on the same machine, which is working fine (can rule out 
hardware issues?).

Here is a list of things I have tried (and none helped)

* Single user mode (rule out initscripts)
* linux acpi=off apm=power_off (rule out power management)
* Boot into knoppix v 3.3 (works without a problem) and do an
  "apt-get upgrade" of the debian installation (on the hard disk).
* Use a older kernel (2.4.25-1-386), instead of my usual 2.4.26-1-686.
* I have also updated the kernel image, etc. (after going through a few
  hoops) to run mkinitrd from knoppix)

All these have failed. Any suggestions?

I have a Intel 2.4GHz processor, 512 MB RAM.

- Murali