I loaded another SL project (termed Proj B) that was compiled on my personal laptop. This project was re-compiled well on my company's CPU. However the SL project (termed Proj A) gets the problem as shown above. I compared both References and codes, and found no difference actually.
Something is strange. Even though the Designers can be drawn on VS, the project compiled "successfully". If I run debug, all of the pages display correctly.
I wish ESRI support team can answer my Q. Thanks.