Appleworks problem

[Stephen Foster]

My 13 year old son is taking a course offered via the internet 
locally. When he tried to submit his first assignment (done in 
Appleworks, saved as a Word document) he kept getting an error 
message to the effect there was an incorrect character in the 
filename. There was nothing special in the filename unless there's an 
invisible character. I tried several other formats but received the 
same message. Perhaps the problem lies in the receiving programme? He 
was using Explorer and o/s 10.1.5. Any thoughts? Thanks, Stephen
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"A man cannot step into the same river twice; for neither is it the 
same river nor is it the same man." Heraclitus c. 540- c. 480 BCE