ParsonsMatt
Alas, Tyranny
That's not freezing, that's just bouncing and muting. If I have a track with lots of plugins and I mute it, the CPU load is still as high, but I froze it, it would drop as it would be like if plugins where not active (at least that's how it worked in Cubase sx3)
In reaper, muting a track stops the plugins from taking any processing power. At least, thats how I think it works.