Crystal Reports Beginers question

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   Hi all,
I've just started working at a new company and they use crystal reports (that i've never used before), so im currently on the learning curve to get it to work.
My problem is that I cant seem to get Crystal reports to traverse over multiple Database tables (via ODBC).
If I say do....
{table1.users} = {table2.users}
It nukes my entire worksheet so nothing will render other than standard labels.
anything I reference from the first table, will work perfectly, but if I try and request or manipulate any data from any other table - everything dies.

I can see the tables fine in the editor, ODBC is running ok and the db itself is fine and intact - Crystal reports was able to work out primary keys/ links and it works fine on other projects - that to all intensive purposes appears top be identical.

Now I *know* it has to be something really small and stupid that i've missed, but due to the fact I dont know the product well enough, i'm not sure where or what it is.

Any ideas?

Thanks in advance!