Sequencing IBM SPSS Amos 21 error occurred

Hi,
I am beginner in Amos, just started to learn new concepts in details. I ended with an error message when I try to display a thumbnail in Amos. I have no idea why this happened. How to solve this error? I appreciated if any could solve my problem. Thanks in advance.

Amos
An error occurred while attempting to display a thumbnail for the file. Ex05-a.amw.
OK
