[blue68f100]

Your problem also is hardware related, maybe thermal related. Over time thermal cycles loosen componets and cables. Opening one up and removing and reinstalling cleans the connections.

Since the 4400 is an older unit, I would do a through cleaning, re-seat the ram, re-apply thermal paste on the cpu/heatsink. Also check and make sure the fans are in good working order. If you can get access to the recovery console there is an option to reinstall and clean install. This will auto load if there is a problem booting. If you do not have access to it inticates toward hardware. The watchdog bios will try to boot from another HD if it fails to get a good boot signal after a set period of time, normally is 5min. Failing power supplies can cause havic too. If you have another unit you can use for parts, would be nice to eliminate the ram and PS.

The procedure to involk the recovery console is posted in one of the Guardian threads. Use the search feature on this forum to locate it. I would only do it after eliminating the hardware.