Cannot open graphs in Power Point 2003

[Patti]

In some presentations I cannot open existing graphs.
Even if I create a new graph and then close it, I cannot
get back into it. I get the message 'the server
application, source file, or item can't be found, or
returned an unknown error. You may need to reinstall the
server application."

How can I get around this? I've reinstalled many times
and it does nothing.

Thanks!!!