What sound card are you using?

Adding reverb to a few tracks should NOT cause that. Especially since you are working in a very small project with only 3 audio tracks.... that should run flawlessly even on a factory card with MME drivers.

Another possible work around is to place the ONE reverb into a buss rather than two instances into the tracks.

The issue sounds like it's more sound card related than memory.

Let us know how this issue resolves.

You can find my music at:
www.herbhartley.com
Add nothing that adds nothing to the music.
You can make excuses or you can make progress but not both.

The magic you are looking for is in the work you are avoiding.