[racket] frustrated with error message

Hello

I am teaching dr. Scheme to high school students and recently have had  
many students lose their work when their Scheme file cannot be  
opened.  The error given is:

insert-file in text%  error loading file (read from file failed)  ===  
context ===

Any ideas what is causing thi?.  It sometimes happens when they are  
inserting images they have found from the internet but it is not  
consistent.

thanks

Erwin Hildebrandt
River East Collegiate