NMM an exception has occurred in the script

[StainglassBandit]

I recently ran into an issue where the game crashed upon trying to close it. No big deal right? it happens, only when I went to start the game again steam had seemingly forgotten all the files existed or were even downloaded. So I did a reinstall and recovery, THEN FOUND OUT a few of my mods had broken. I tried to install them again and was greeted with the An exception has occured in the script message. I Figured the problem was with the game files having to revalidate themselves so I uninstalled the game and all my mods to start from scratch. This morning after a fresh install of the game I went to install the mods and was yet again greeted with this message. Could anyone help me out? I'd like to be able to play again.

[dubiousintent]

From what I can see in that error message, your problem is primarily one of "permissions".

 

As of 08 May 2018, the Nexus has changed some site security to come into compliance with the new "European Union General Data Protection Regulation" (EU GDPR) rules. This breaks older versions of NMM and other tools using the older unsecured API. It is usually reported as being "blocked by the Windows firewall" or causing a "script" or "W3C XML Schema" error installing mods. You will need to update it from NMM on GitHub or this Nexus NMM download page. Check the version numbers between those sites and use the latest (v0.65.4 at this time). Please see this Nexus site news article for details.

A Working "unofficial" fix (confirmed) to login to Nexus with MO or older NMM versions is available in this Reddit thread:
Classic Login fix for MO1/NMM.
Note: this "fix" reverts to using the older, unsecure API at a fixed, no longer used IP address (instead of the address returned using DNS), and thus negates the EU GDPR standard. It could get shutdown without warning 25 May or after as that is the EU deadline for compliance and Nexus is hosted in the United Kingdom. Use at your own risk.

Some people are finding that even after updating NMM to v0.65.4 they still get a "script exception" message when installing some mods (such as UIO and MCM). This seems to be resolved by this suggestion from user ElysianMod:
* Run NMM as an "Administrator privileges" account.
* Go to NMM "Settings".
* Enable "Add Shell Extensions for Supported File Types".
* Then restart NMM.
(Supposedly this fix will be included in the next "unofficial" update to NMM on GitHub.)

IF that doesn't resolve the problem then:

 

Did you install Steam to it's default location? If so, please see the wiki "Installing Games on Windows Vista+" article for why the original default Steam behavior of installing games to the "C:\Program Files" folder tree was bad (they learned better, and don't do that any more); and why "disabling UAC and running as Administrator" is NOT sufficient, with instructions how to move it. This is the single most important thing you can do to fix and protect yourself against problems in the future. As much of a PITA as that is, it's never going to be any easier than now. Please see the 'Restoring to "Vanilla"' section of the wiki "FNV General Mod Use Advice" article as well.

 

-Dubious-