I can not open my excel files
 

when I try to open any of my files in excel I get this message - "this
document caused a serious error the last time it was opened - would you like
to continue openeing it?" If I say no and try to shut down - the program
just hangs up - if I say yes - it does the same thing. I have to go to task
manager and end the program to get it to close. This is happening with all
files - even if a create a new one and save it and close it and try to reopen
it. Can anyone help me.