If you haven't already, you might wanna try these tips
http://music.tutsplus.com/tutorials...formance-in-propellerheads-reason--audio-1075
What also helped my PC to stop from glitching was:
1. stop multiple processes (i.e. running internet and firewalls, etc.)
2. If using quite a lot of channels on the SSL (incl several busses), mute the ones you don't need to hear while arranging your track.
3. Muting in the sequencer uses less CPU than muting on the mixer (at least in my case it did)
4. I use a lot of automation. Mute it when you don't really need to hear the effect when working on your track (don't forget to unmute it when you want to export your track
)
5. If possible use an Audiotrack instead of a mix channel.
6. If you don't use a device or effect (let's say Thor and Alligator; these use a lot of CPU, I figured), delete it and it's tracks.
Keep your rack and sequencer as 'clean' as possible.
Hope it helps u out!
Rgrds Ronald