Game crashes when pressing "Continue" after installing "Secrets of the Revolution" DLC

[Tina]

So, Assassin's Creed Unity _was_ working just fine for me. I'd beaten the game, then bought the "Secrets of the Revolution" DLC on sale. (I already had the "Dead Kings" DLC, in case you were wondering.) I start the game, Steam gives me a message saying I will need to enter a certain key in-game at some point to activate the new DLC. Okay, sure. I copy the key and press "Play" on the message window. (Steam also gives me a pop-up message as the game starts saying the same thing, but as you'll see, the game never asks for the key. I'm not sure if any of this is relevant, I'm just trying to be thorough.)

So the game starts up, I press "A" on my controller (well, X, as it is a DualShock 4) to go past the title screen, and then again when it says "Continue" and shows me information about my save file (62% complete). Then, the game starts loading... and while loading, it crashes. Every. Damn. Time.

I've tried, just in case it helps, entering that key Steam gave me into Ubisoft Connect (which seemed to recognize it as a key for the Secrets of the Revolution DLC and activate it, but the game still crashes just the same). I tried unchecking the Secrets of the Revolution DLC in the Steam game properties under "DLC" (It seems to count it as two DLCs, one for Secrets of the Revolution itself and the other for its "Uplay Activation," so I unchecked both). It still crashes. I tried verifying the game files. (That time, after verifying the game files, it asked me for admin permissions and did some "first-time setup" when I started the game, but it still flamin' crashed.) No matter what I try, the game crashes.

(I suppose the most obvious solution would be to uninstall the Secrets if the Revolution DLC, but I can't figure out how to do that, hence why I unchecked the DLC in the game properties and tried launching it, no luck, and then tried verifying the game files with the Secrets of the Revolution DLC still unchecked and then launching the game, no luck.)

I can tell you that some of the crashes have been accompanied by an actual error message, a window with the heading "ACU.exe - Application Error" and the message:

"The instruction at 0x00000001427484C2 referenced memory at 0x0000000000000000. The memory could not be written.

Click on OK to terminate the program"

(I'm not entirely sure the first memory address is consistent across cases, as I've only gotten this error message twice--other times it simply crashes silently--but the second memory address, the one that's all zeroes, definitely did stay the same in both cases.)

I'm losing my mind, here. What haven't I tried? What do I need to do to get the game working again? Please help! (And I really would rather not lose my save file--100 hours' worth--because I committed the sin of purchasing and installing DLC.) Thank you!

[Tina]

Well, for some reason, the game works again. First, I contacted Ubisoft Support, and they sent me their usual boilerplate response for problems like this, directing me to this page: https://www.ubisoft.com/en-us/help/connectivity-and-performance/article/troubleshooting-technical-issues-on-pc/000061047 The last suggestion on the page, however, "disable background applications," was something I hadn't actually tried. That sent me to this page: https://www.ubisoft.com/en-us/help/connectivity-and-performance/article/disabling-background-applications-on-pc/000063761 which directed me here: https://support.microsoft.com/en-gb/topic/how-to-perform-a-clean-boot-in-windows-da2f9573-6eec-00ad-2f8a-a97a1807f3dd

So, I followed the instructions for running a clean boot of the system (disabling every service and startup application, basically, then restarting the computer), and I ran Assassin's Creed: Unity, from the Start menu this time (instead of from Steam, since it wasn't running yet). Steam started and wanted an update, then the Ubisoft Connect launcher ran and updated itself as well, and I had to log into my Ubisoft account (of course... what a pain), and... the game ran. It actually worked. Even the "Secrets of the Revolution" content seemed to work (at least, I had a new mission on the map, I'm assuming that's the content in question; I haven't actually tried the mission yet). (Oh, and it's worth noting: Steam didn't have its usual popups and notifications about a key I need to enter or anything like that, the ones I've been getting since installing the Secrets of the Revolution DLC. The game just ran without any problems.)

So, I tried re-enabling all those disabled services and startup applications and restarting the computer, and tried the game again. It still worked. I tried re-checking the "Secrets of the Revolution" DLC (and the "Uplay Activation" one for it) in the game's Steam properties and tried running the game again. and it still worked! I don't know what did it, maybe it was trying the clean boot, maybe it was those updates to Steam and/or the Ubisoft Connect launcher, but the game definitely seems to work again, and I haven't lost any progress. Whew! Not sure if this is helpful for anybody else--hopefully I'm the only person to have this problem--but there you go.