Thanks for drawing attention to this. This stuff is specifically why the MULTI sub-team was created, so hopefully some of those members with FRED skills may be able to help investigate and see if these are code bugs we introduced or just things we need to clean up in the multiplayer campaign.
The STD thing is really just the fully qualified name of the Exception class, and is short for 'standard', as the exception is part of the C++ standard library. The fact that it was thrown means the game code reached a point where it didn't know how best to proceed, and because of that, exceptions will generally result in the game exiting, so it's no surprise he is booted when it occurs. I suspect that error might not be campaign related, although I could be wrong. At best, if there is data out there causing an exception, we may be able to handle it better in the code. But we should also correct the mission/asset data if it's the root cause of the issue here.
The second problem to me looks more likely to be an asset issue, and it is giving a clearer error message, albeit still one without a chance of recovery. Surprising since I imagine these campaigns haven't exactly changed much and at some point in the past these issues must not have been truly 'unrecoverable'. Will have to investigate what is leading to that problem now.
A debug log would always be helpful, but in lack of one for now, any other details you are certain about regarding your installs would be helpful. FSO version, MediaVPs version, any other mods active you might have forgot to mention. The debug log typically contains all this, which is why it's usually requested, but if you can say for certain there are no non-standard mods in the FS2 folder for now, we can go from there until a debug log is available.