50 tracks?
If you're using that many tracks - I would get more ram. Especially if you're trying to use FX for them all. You're asking a lot of your PC.
...and I would try using a different program. I'm a big fan of CEP - but I would think something like Cubase would work better when you have that many tracks in one session....especially when you're trying to put that many FX/Tracks in one session.
Maybe try bouncing some of those tracks/takes down before you start putting reverb on them.
Most importantly - organize yourself. If I were you, I would have a folder for the song. Every now and then, save the different takes and individual components of the song (and the session too!).
...but I can admit - a song with 50 tracks is out of my league. I'm more on the hobbyist tip. I feel like I'm doing big time shit when I have 10 tracks

- hopefully someone else w/ more experience will hop in.