Ditto. Confirmed as host of mutiplayer, no other players joined. Allowed for mutiple autosaves and a manual quit-save. All of the savefiles will not load in single or multiplayer.
Update: This appears to be tied to loading a savefile in multiplayer first. After the bug appears, NO savefile will load in SP or MP.
As a workaround, I tried loading a MP savefile in SP, first. This work, and I exited. I then hosted a MP game and loaded the SAME savefile without issue.
It appears to be tied to MP loading. SP loading somehow prepares the memspace, allowing the load. MP is only able to utilize the resources once they have been prepared (it seems)