I think I may have found a (temporary? it's yet to break on me) fix! I opened the launcher 'steam_4.1.1.1473368_alteredFiles' file located in the appdata/local/larian etc. cache directory, and it pointed out the file DWrite.dll in the game's bin folder was apparently the altered file. I moved it elsewhere and the error message no longer shows up and an issue I was having with a CTD bug disappeared.
Dunno if this method might help others find what their specific problems are but thought I'd report my findings.
I'm going to try this next, thanks for letting everyone know. I had everything fixed, but after hotfix 20, it came back. Did everything the support page said, but no luck. Also that first paragraph on the support page (see below): what am I supposed to do? I tried deleting the folder, or the alteredfile.txt thingy, but it refuses to be deleted (it comes back, appearing outta nowhere, even after I delete it).
"In this case, there should be a log file listing any files in the install folder which are not expected, as well as files in the Mods folder. Copy %LocalAppData%\Larian Studios\Launcher\Cache into the location bar in Explorer and hit Enter, then look for a text file named for the platform (steam/galaxy), the game version number and ending with '_alteredFiles.txt'."
Okay, yes.... aaaaaand? What do you want me to do with this, @Larian ? Delete it? Rename it? I find this very unclear, since I'm not super PC literate. Anyone help?