Midi Problem

Honestly I don't think there is enough information to go on to make a solid response.  First thing I would check is that you didn't move the MIDI track slightly by accident.  Perhaps if you nudge the drums a little by using the number pad everything will line up?

nope.... the problem is latency... usually the result of trying to use a factory sound card to render a synth such as the SI drums.  It takes time to process the synth drums but it takes mo time to process the guitar track since it's already audio. the factory sound card uses less than optimal drivers and circuits, so you will have that latency.

You can try adjusting the latency slider a bit to see if you can get it close enough to work with....or, you can look at the aftermarket sound cards commonly called interfaces. Get a nice USB based interface that uses ASIO drivers and the latency will drop to such low levels that it will practically disappear.

Most of the long time users here have a decent interface and we love it. It lets the DAW work the way it's supposed to.