Include your system specs
Answer: ever used a custom ui?
This error can happen because of several different reasons, including 64 bit and a 32 bit environment conflicts at the .dll file.
You could try updating your drivers, turning off security software, running in compatibility mode, running as administrator, setting to DX9 on the Patcher Options, shader 2.0 or higher, re-install Strange UI and uninstall properly (deactivate) or ask Santa for a new Nvidia graphics card… but until you reveal more information it’s wasteful guess-work at best; probably why you didn’t get much feedback 