DNS problem

Hello again I having a wired problem if use nslookup to check some changes that I made to the blackhole list.First I'll check a site that I know has access throught our sever and it would time out. Then If I'll try it 10 seconds later it would work. Isn't that wierd. But my blackhole list site would be find and not work. What could cause this problem.

AOJMOJ :confused: