Can anyone explain what might be going on here? When the wheel on scroll mouse is used to scroll up and down a Word 2003 document occasionally it copies lines of text. These copied lines are not permanent, is you stop scrolling the duplicates disappear and is you save a document the duplicates are not saved. If the scroll bars are used instead of the scroll wheel there is no problem at all. So far a new mouse has been tried and Word has been reloaded, neither has resolved the problem. No software has been loaded for the 2 mice used, just windows drivers. This problem seems to be intermittent as it doesn't happen on every document, sometimes the same document exhibits the problem, sometimes not, its weird. Anyone any ideas?