It sounds very much like you're using a lot of free VST's. There's not a lot the guys at Acoustica can do about the stability of the VST's. Using outdated VST's is gonna cause all kinds of trouble.
I HIGHLY recommend running only VST's that are compatible with whatever version you are using: 32 bit VST's in 32 bit Mixcraft, and 64 bit VST's in 64 bit Mixcraft. Mixing 32 and 64 bit systems is just asking for trouble. And even if the VST's are stable, any time you involve the Bridge, you're adding another point of possible failure. I'm finally completely 64 bit now. There are lots of threads out there with answers for replacement VST's for most VST's out there (I.e. VOS Thrillseeker VBL, etc.).
Yeah, there's generally no problem running 32-bit plugins in 64-bit Mixcraft, aside from a bit more CPU overhead. And some plugins are way more CPU hungry than others, so loading a bunch of 32-bit heavy-CPU-users into 64-bit Mixcraft might ding your audio/CPU performance.
In this particular case, he was using a plugin called Headcrusherfree and also DensityMKIII. I have DensityMKIII and I'm not seeing problems with it, but he said that not using both of those plugins helped him.
He was still having some freezing, and then he found that running as an administrator helped with that. I'm not sure why that would be the case, it's possible some plugin was still misbehaving.
So, I get the dreaded "not responding" circle of death A LOT with Mixcraft. And I mean a lot. And I'm always forced to shut er down and "wait for Windows to report to Microsoft". For what purpose I do not know. Doesn't matter if I'm saving, deleting a track, or switching plugins. Pretty much everything is fair game. I don't know if it's a Windows issue or MC or both. I've optimized the best I can, but it's one of those chronic problems I've learned to live with and work around. I don't even bother submitting tickets for it. Doesn't seem worth it anymore. But sometimes I stop and wonder why. I check YouTube videos for a solution, but that's usually apples and oranges. Anyone else live with this affliction?