Excel 2008 conversion problem

When I open an 2004 version of excel for mac file using 2008 version, the file opens with formatting but you can't see the data. If you click on a cell you can see the data at the top of the page but not in the cell. also some of the formatting options(bold, underline and some others) are not allowable. These are files created by someone else, not simple files which work fine. These files work fine in windows excel.