Thanks for your response.
I am sorry that I can't post the query here.
I tried to simulate the issue in test, but couldn't.
But beleive me, it's a strange problem. And one more thing...
When I simply quey using "UNION" this issue occurs.
But when I add "top 10 *" with same query, it just works fine.
Anyways, when I am free, will try to put those records in some dummy tables and simulate the same error so that I can show you the error.