Rpg Maker Developers Group

I am frustrated to the point of tears now. I'm trying to install a sideview battle script (Minkoff's Animated Battlers Enhanced to be precise), and every time I add it above the main line in the script editor, my game runs fine up until I try to trigger a battle, I get an error message like:
"Script 'Animated Gradient Bars' line 159: NoMethodError ocurred.

undefined method 'viewport2' for nil:NilClass"

I haven't touched the script, I just copy and pasted it into my script editor, so I have no idea why it's giving me an error.

Even more frustratingly, the script works just fine in a blank new project, so I tried rebuilding my game from a new file too, but nope, after I've got all my maps and events and actor and everything set up, the same error happens again. Even if I take out the Animated Gradient Bars code and try again, I get the same error but with a different page of the script.

This has happened with other scripts too -- namely Law's Custom Save script. I have no idea what it is about this project that's giving me so many errors when I mess with the scripting, but it's killing me. I'm so very close to finishing this, but I absolutely need a sideview battle system, and I just can't get it to work. Is there anyone out there who can tell me how I can fix these errors, or maybe look at it to see what the issue is?

I've uploaded my demo so far here if you want to take a look at the error for me (select save file 2 and go through the door in front of you to trigger the error. Also please ignore the clearly unfinished sprite, I haven't finished making the character yet, as you can see by the way it flashes between two characters).

Thank you from the bottom of my heart if you can help me out here. I only started teaching myself RPG Maker stuff a few days ago and while I've made great progress in my understanding, resolving script errors is so out of my league right now, and I haven't been able to find any resources on the matter.