dragging the timeline/playback suddenly became slow & choppy

PA_ThePhilosopher

Hey guys,

I was wondering if any of your have experienced this when making an animation. Normally I can play my animation and drag the timeline marker smoothly (w/ the viewport mode on basic texture shaded). But I have noticed recently on my project that now it has becomes very slow and choppy. Now when I play back my animation, it skips frames and is just not as smooth as it used to be, which makes it difficult to review changes.

I was curious if there may be a common cause for this kind of slow-down? 

Thanks.