Back and Forth we go

People can be so frustrating. Usually it is because they can't make up their minds and flip-flop from one thing to another. Lately it has been mostly people at work. If you didn't know already, I am a project engineer for a small company and it seems lately that I have to hold peoples' hands to get anything done. The following may not make sense to anyone but I have to vent anyway...

First everything is okay and then someone from QA gets a 2nd look at the drawing and decides that the plant can't make the part after all. They were making this damn part for the past 40 years with no problems, why all of a sudden now. Or they can't remember talking to me about the problem on the phone the day before and I get the lame excuse that they weren't paying attention to what I am asking, even though I am asking a direction question. I know what I do in the business unit is benefical, but I can't seem to get my job done when I can't seem to get answers from other people. If I am not waiting on one person, I am waiting on another. Blah...