my husband changed job during waiting for interview and didn't notify embassy the change. When he was taking interview the officer called his former company but no one picked up the phone because that company was bankcrupted and his direct superviser had already immigrated to Canada one month ago. this brought some trouble to my husband but fortunately he made it. He just told the truth and the officer seemed understood this popular situation in IT industry.
Immigration interview is totally different with the US F-1 visa interview. As long as you are truly qualified, you dont' need to worry at all.
Prepare well that you can explain your situation clearly and reasonably, otherwise they would be suspicious to your documents as well as your capability.
Good luck.