I am trying to subtract a rack from a blank. Initially it works good, but at some instance, it does not work showing the error "OPERATION FAILED DUE TO GEOMETRIC CONDITION". I have understood that it is because the volume to be  subtracted from the blank was very small.

Now the situation is different, when I try to combine (subtract) , the blank changes in to some pane or sheet like geometry. I am not able to understand the logic behind this transformation. I am attaching the part I am working on.

The part contain two bodies. Try combining the rack from the blank. ie, select, blank as the original body and the rack as the second body.

I am using SW 2008 running on Win XP SP2 , in my workstation.