Word 2000 problem with Autocorrect and expanders

I recently purchased a new computer (Dell XPS) and installed my Word 2000, which is also linked to ChartScript from my MT job. I am encoutering an intermittent problem where I will type in my expander, and once it expands out, it automatically back spaces, which then connects to the previous word making one big word, and obviously a misspelled word. Once that happens, any double spacing or tabbing in the rest of the document then starts jumping back a space also. I have checked everywhere for a setting glitch, but I am coming up empty-handed. Can anyone offer any clue? Like I said, it doesn't happen all the time, but when it does it drives me crazy!
Thanks for any help.
Cheryl