I have a late '09 IMAC 21 w/16 Gigs of Ram, Office 2011 and Yosemite and all of a sudden can not type anything in a cell or even type in 'find'. Word works, but any Excel file is the same. Interestingly, when I copy and paste from a cell, it pastes matching format, which it never did before. Have made no changes that I am aware of.