I'm having the same problem.
Using build 847, MS Word 2003 (11.8307.8221) SP3 part of MS Office Professional Edition 2003. English version but everything configured for Portuguese.
I don't know if you noticed but all paragraphs with the bug are formatted as Arabic or Hebrew Language, therefore the writing from right to left and the last character in the beginning of the sentences.
Selecting the text and changing language partially solves the problem, the tricky part is that the problems occurs randomly, hard do identify where, in long documents, the problem is, and with so many inserted text and tags is somehow hard to select the right text without changing other correct and desired formatting. Well, just a clue.