Problem with rotating along x-axis

Hello!
Hopefully, someone can help me with this. The problem is quite simple, yet I cannot seem to find a solution.
The thing is that I want to rotate something along the x-axis. I use a keyframe at frame 1 and another keyframe at frame 75. I want the object to be rotated by 180° on frame 75. So I keyframe 0° on frame 1 and 180° on frame 75.
But then the strange problem occurs. The object makes weird movements. It wobbles. It does not only rotate on the x-axis, but also on the y- and\or z-axis.
I have had the same problem before while working on a different scene. And in the other scene, sometimes the same problem also occured when I tried rotating along the y-axis. Z-axis rotations worked fine, though. Also, this doesn’t seem to be a problem with 180° rotation only, because in that other scene, I used rotations with less than 180° and the object didn’t rotate along one axis either.
I am using Blender 2.68 (a (I guess)).

Blend file ?

I hope this works. I’m not sure if I can attach the file like that.

Attachments

untitled.blend (703 KB)

Before you keyframe the animation apply the objects current rotation (Ctrl+A / Rotation while in object mode)

Thank you very much! It definitely worked fine!