Perhaps you need to reset your activation. Choose Help > Deactivate then restart Premiere Pro. Then choose Help > Activate. See if that solves your issue.
Please provide hardware details... especially are you using an external hard drive?
Nvidia 460 SE
SSD - Boot Drive/Programs
HDD - All media files are stored
1. Can you open the files into a new sequence without the error message "Error decompressing audio or video"?
2. Do you have incremental backups of your project file - so that you can switch back to an earlier version?
So, I can open another sequence and import other formats like .MOV, but I can't import the other files.
No, I don't have incremental backups of my project file.
I guess all of a sudden, Premiere suddenly decides it doesn't want to read those files anymore.
Read post 1 dude. That's the solution.