throwaway

Yes, but that's quite big... as you would have to have the unchanged mods, unchanged BWS files(fixes) etc. So in conclusion:

You need to start a new game...

You also have the possibility to start a new game in the BGII - SoA, but then your party won't be unchanged, as the BGT-Tweakpacks NPC component only effects the party members that are in the party during the transition, but you won't be going through it so, your party might change a bit...

I was somewhat afraid of that. This whole ordeal reminds me too much of this xkcd.

Anyway, the original problem that was the root cause of all my other problems is that the game crashed occasionally while resting (game would freeze as soon as I pressed the "rest" button, before anything else happend). This only started happening after I had already been playing for a while (never crashed at first).

Now, I realize this might be a slim hope, but is this perhaps a known (and hopefully easily fixed) issue? My google-fu failed me here as well, and I would hate for this to happen again in a new game.

Well, if the install order is changed at all, you need to start a new game, to prevent the dialog file from being full of cheese... yes, that mans head is on a stick because he didn't believe this fact(of Infinity Engine modifying)...
(this picture was censored because of rumors that the trial was staged, the was jury bought off and the executioner had a day off that day)

I see. This is.. somewhat troubling. So if I manage to reinstall BWP with exactly the same configuration that I used the first time, I could fix the problem?

You need to start a new game... as in not load an old save, but start a new one from the beginning... as your savegame has a text file that's not patched by any mod if it's started before you install the mods... and so all the text is garbage material.

I wish to clarify that the game was started after I had installed BWP the first time. Might this be because the exact mods installed differ between my BWP installations? As in, might there be a mod extra or a mod missing from my current BWP installation, causing this strangeness? I'm not entirely certain this installation of BWP ended up exactly the same as the one before (and seeing as how I shift-deleted the whole previous BG2 category, I cannot check what mods I had installed before either).

Well, there is a way to fix your saved game, but you have to work quite a lot and something odd will probably remain.

You could use near infinity to fix all wrong references. Every time you see that something (an item, a creature, the worldmap,...) has problems with the name, description, ..., you have to open your saved game file with NI, (some things are in the .gam file, others in the .sav), DON'T edit the text, but you can open your dialogue.tlk file in another window (alwayas with NI), search for the right names, copy the string number, and change the number of the string in your .cre, .itm,... file with the right one. But be careful not to edit the dialog.txt file, otherwise, you might fix your game, but all other games you will start will be messed up

Yeah, ouch. I've poured maybe 20 hours into the save so far, but this solution sounds even more tedious than starting a new game.

Thank you for your suggestions so far, anyway.