This looks like you are using ReaPack v1.0 but the data files were actually created by version 1.1. Updating manually should fix this: just overwrite the existing DLL file with the new one.
I made changes in v1.1 to avoid this situation in the future. You can check which version you currently have at the bottom of the menu (Extensions > ReaPack).
(Note that there is a dedicated issue tracker for ReaPack
here – this subforum is for REAPER's)