I'm finding that, with a simple filter on, dragging over cells hidden by the filter changes the values in the hidden cells too. This happens to some users in the organisation while for others they do not experience any issues.We all use Office 2010.Is there some settings not configured right for some users?

Not completely sure what is going on. I would have to know for sure what kind of data is in those hidden cells. Numbers, text, formulas. If it's formulas it may that automatic calculation is turned off on the computers since filtering data with formulas will calculate with every filter and cause it to run slow.