Audio pitch shifting when importing video file into project... why?

The pitch is shifted lower. not much but it makes it sound like it's dragging which now that I think about it... maybe the video is slowed down when I import and that is why it sounds like that... either way, other files I have imported does not changed but this file does. It originally was in AVI format and I converted it to MP4 "HD" becaue FCPX wouldnt import the AVI file. I've tried all I can think of to change the pitch of this file back to normal but I can't get it to the right pitch of the original file. Someone help me please. ps. I am new to FCPx and Mac so please take that into consideration.

Convert it to ProRes, maybe? What is the frame rate of the video, and the audio sample rate of the audio?