I have since found that we have a difference in the Number format set under Options. I have numbers set to 1234, he has 1234.56  If he resets to integer, he gets results too.  But this report has to be distributed, so it has to work whichever way.  Anyway, it works ok with the other two subreports, which are very similar. And the linking parameters are all primary to foreign keys, which are integer numbers.

This is actually distributed to work with a bought-in  Oracle system which has a run-time version of Crystal embedded to run these reports I write. I cannot change anything in this system, so I have to get it right here.

Once uppon a time I have had an issue where the report was working in my company environment but failed to start at customers...

I solved it by doing following:

I've saved the subreports into separate reports and I proved them to be working fine in all environments.

Than I made a copy of one of them, I got rid of all the content and used it as a canvas for the subreports. I have added all the subreports to the canvas providing accurate parameter links. I've test it few times and than I've saved it. It started to work in customers environment. Until now I don't know why it failed to start beforehand.

I hope that will help :)

Cheers