When I or a user changes the version of a Word 2003 doc to 2010, all pictures and charts suddenly gets borders.
How can this be avoided?
This is because of a change in how Word 2003 and Word 2007 internally store tables. In Word 2003 tables do not have borders by default, but in Word 2007 they do. Consequently tables with borders set to "default" in Word 2003 magically get borders when converting to Word 2007.
Unfortunately there is no way to prevent this, short of upgrading all of your documents to Word 2007, correcting the borders and then deleting the old copies.