After a search on Google, I found that various people had this on Linux, but… (plot twist ensues)
I’M RUNNING WINDOWS!!!
CAudioSourceMemWave (garrysmod\ui_hover.wav): GetDataPointer() failed.
Yes, I have tried verifying the integrity of the cashe
EDIT: Wow, all I had to do was delete my garry’s mod folder after deleting and then reinstall.