When calling a form from a thread. It just hangs. No error detects or etc

Sounds to me like you have either a dead-lock.

What about to debug and go through your code to know in which method has infinite loop or deadlock like Comatose says...

ya thats a deadlock. A thread is running at back. when i cal a form from that thread. Form hangs. I think it does not go to either side coz form is actually a thread na of ui type so it hangs. NOw tell me the solution. Code goes like this

Thread in some different class than UI

     if ( some condition )
        dim abc as form
        ' Here form just hangs and nothing ahead. any solution?
     end if
 end while

Should we understand these lines of codes!!