No need for a separate installation of reason. Just find the reason application in Finder...right click on it and go to "Get Info". Then check the box that says "Open in 32 bit mode".
I'd recommend you just use the Ableton 8.4 beta and take advantage of 64 bit rewire power though...
You don't open rewire in 32 bit mode on a PC to my knowledge. You have to have both apps that can rewire to one-another as both 32 bit or both 64 bit, can't intermix them. I see the newest beta works with Studio One V2.5 now = so now I wait for 9.0.3 with this fix so I can see what all the hubub is about with rewiring apps
http://www.darkenedsoul.net - main website
Ableton Live 8.x/9.x : NI Komplete 8 : Home built 4690K 16GB 500GB SSD, 1TB 7200, 2x2TB.