Oh, I found the reason and solved the problem.
Yesterday, I built the exchndl target under TDM-GCC-4.7.1-sjlj which link against MinGW official libintl. But today, I forget to rebuild exchndl under PCX MinGW GCC 4.6.3. Aha, maybe ABI conflicts between GCC 4.7.x and GCC 4.6.x.
After build it under PCXGCC4.6.3, the Error dialog has gone.
Sorry about the noise.