Why won't my upgraded version of Office For Mac work?

Recently I upgraded my 2008 MacBook to 10.7.5 and discovered that I also needed to upgrade MS Office for Mac 2008 to Office for Mac 2011. When I open Word documents that people send as attachments in email, all I see is a mostly blank page. Should I have removed the 2008 version before installing the 2011 version? Or is the problem caused by something else? The Microsoft support communities haven't responded to my question. Can anyone in the Mac support community help?