[ivansc]

Give us a rundown on your computer, operating system, reaper version etc and of course what audio/MIDI interface you are using.
SD3 does use rather more resources than SD2 just in terms of the actual core program, but I would hope (since I beta tested it extensively) that it is something else causing your problem.
And of coruse do the obvious things like running reaper and resplendence.com`s latency checker at the same time (if you are using a PC) just in case one of those wonderful windows updates added something "interesting" that is affecting your overall performance.

Besides the crash log, are you getting any message window from either reaper or SD3 when the crashes occur? Also did you try using a clean portable install with JUST SD3 scanned into the "new" reaper? It could still be as simple as something silly in your settings, although I doubt it.