Yeah, I bet you have installed one or more scripts and not gone through and set them up properly. Several of them use switches and/or variables, and you are meant to allocate unique switches/variables for their use - naming them in your switch/variable list so they don't get accidentally used for something else, and then editing the script to tell it which ones you've allocated.
Yami's Overlay map is one that does this, and people commonly have this issue because they haven't taken the time to read/understand the instructions and set it up. But there are many more.
On the bright side, it's good that you discovered this NOW, as it would have had you pulling your hair out if you'd gotten much further into development and it started happening.