I then went to look at system logs, and found that at the point of a crash there was an error iirc relating to not being able to set C locale, or something on those lines. I don't recall the exact wording, and trying to find it again after rebooting my machine would be a little too much work. This gave me a clue about the issue, though, and I realized I had recently been messing with KDE's region/language settings, and they were a mix of a couple different locales—because I mostly prefer British English but don't actually live in the UK. I set it all back to my default locale (in my case British English), rebooted, and everything seems to work again now.
So anyway, I'm writing this A) as a heads-up to the devs that there could be something a little wonky with the locale code in your newer builds, since only the current stable Diva and Satin versions appeared to be affected out of the ones I tried. And B) in case any other users are having unexplained crashes with these plugins, this could be another avenue to look into... Sorry I can't provide more precise information, the issue on my end is now fixed and I'm not keen on trying to replicate it again...
