Problem with Office 2007 files opening

We have some Access and Excel files in our office that are “shared" meaning
that multiple people can have them open at one time…editing…saving…all at the
same time.

Now that we're upgraded to Office 2007 sometimes when I try to open the
“shared� files…..the program “stalls out� for lack of a better way to explain
it.

The file acts like it is going to open, but never does. Then if you
minimize the program and then click on it to maximize it, all of a sudden
starts loading the document and opens it, but you have to “manually
jump-start� the program in order for the file to open. I heard that someone
else has this problem all of the time when he opens any kind of file.

Any ideas on what is causing this problem and how we can solve it?