>Well, all the computers are working on the same database, so in that case i should have the problem on all the computers.

Assuming these are totally identical queries (they'd have to be to discount an index problem, which is still by far the common problem), I would look at just how the different result sets vary, there might be a clue there; compare them. For example, I've had it happen a couple times that an occasional odd user was running apps with different EXACT/ANSI/DELETE settings on (or a few other ones that SQL respects) that could cause different dataset results.

Other problems could be different app versions, or different tables being used called in the SQL, or actual bad data (like with odd special chars in it), or but I assume you've looked into these.