Motorola Droid :: Full SD Card Lag?

I have about 2 gigs of music on my sd card and my phone still runs smooth as silk. Then I put 8 or 9 gigs worth of videos (mp4's) on there and the whole phone started lagging BIG TIME. Like, lagging more than a...Err, slower than a...Well, something. I mean, I'd swipe from one home screen to the next and the screen wouldn't actually change for 4-5 seconds; And scrolling up and down through gchat IM's or in the app drawer was VERY choppy. I tried a power cycle and a battery pull to no avail. The only thing I did before this laggy behaivor started was dragging-and-dropping those videos onto the card, so I tried deleting them, power cycled the phone and now I'm back to the original smoothness.

I suppose I can live without watching videos on my phone (though, they would have come in handy on a roadtrip I have later this week), but has anyone experienced anything like this?