a problem when using postDominatorTree

Hi all,
I’m using postDominatorTree to do some program analysis. My code works well for small tests, but when I run it on real applications, the following error occurs:

Inorder PostDominator Tree: DFSNumbers invalid: 0 slow queries.
[1] <> {0,21}
[2] %bb1 {1,2}
[2] %bb {3,4}
[2] %entry {5,6}
[2] %bb8 {7,20}
[3] %bb7 {8,9}
[3] %bb2 {10,11}
[3] %bb6 {12,13}
[3] %bb5 {14,19}
[4] %bb4 {15,16}
[4] %bb3 {17,18}
0 opt 0x085643e8
Stack dump:
0. Program arguments: opt -load=/home/a_i/llvm/llvm-2.7/Release/lib/ConsDumper.so -consdumper -f -o pbzip2_2s.bc pbzip2.bc -debug
1. Running pass ‘dump constraints’ on module ‘pbzip2.bc’.
Segmentation fault

I have no hint about this. Does anyone know about the reason?
Thanks a lot~

Regards,
–Wenbin