I haven't followed the exp-ex link to see what it says...and I haven't used Word, since Word '97
One thing I recall being an issue was the Auto-Save feature every 'x' amt of minutes (default was 10min (?)). This was set through that abyss called Options somewhere.
I suspect while also viewing --> Start | Run EVENTVWR
the system is BSOD-ing, but b/c of a setting in System Properties, the system reboots instead of BSODing and giving you a STOP error code -- from which, you may get some useful info (an EventID #) to track down the problem
Startup and Recovery Options:
By default, XP is configured that when a system failure is encountered the system automatically restarts. This behavior may at times be desirable, especially if a system is unattended and and a reboot is necessary to restore a system to operation. Unfortunately, it also makes it very difficult if not impossible for a user to read the messages that are presented that may provide clues to a shutdown problem. To prevent the system from automatically restarting:
Right click [My Computer] click [Properties] and select [Advanced] tab.
Click the [Settings] button in the [Startup and Recovery] section.
Remove the checkmark from [Automatically Restart] in [System Failure] section.
Also 97 MS Word has a "built-in" Anti-Viral / Macro virus protection engine...
This can be disabled through Options as well....I'm sure 2003 has something similar, if not even more intrusive/intensive.
Perhaps your system AV software and the Macro scanning module are conflicting.
Word97 was already bloated and trying to be too much more than just a Word Processor (Integrated HTML convertors, AVscanner, OLE object binders, etc) -- I can only imagine how much more-so it's become.