LibreOffice 5.4.2 Calc crashes each time I try to open an existing file - Windows 10 x64

Hello,

I hope someone has a solution for this, as I’ve been struggling for 3 days now, trying to find it and fix it.
I’ve been using LibreOffice, and most of all Calc, for at least a year now, without any problem other than the occasional botched update permission.

But a few days ago, I tried to continue on a Calc file, and it simply doesn’t open. It seems to load Calc, and then immediately crashes and a little window pops up asking if I want to recover any file and/or send an error report. No files are listed.

It does that with ALL calc files. Note that they were created with LibreOffice Calc, so no export from other programs.

I’ve followed instructions on help pages, resetting user profile, deleted all temporary files of all programs, not only LO ones…

Uninstalled, rebooted, reinstalled, same problem.
Repeated all of these things various times with absolutely no change.

All other parts of LO seem to work perfectly, though I rarely use them, it is important for me that Calc works.

All help appreciated! Thank you!

EDIT 1:

Forgot to mention: It leaves a whole bunch of “LibreOffice” processes running and at least one for Calc, too, that I have to force close before being able to try again. Also, I have it installed in Spanish, though I imagine that shouldn’t matter.

EDIT 2:

All parts of LibreOffice have started to do the same thing now. Writer, etc… Nothing works.