@
avidreadr - Try running in Windows Safe mode. Poorly written shell extensions, utilities loaded at startup, and drivers can cause these sort of problems. Box pedlars install programs you don't need to get the kickbacks from the software suppliers, who then do automatic silent updates which breaks programs you do need.
See
Calibre User Manual->Frequently Asked Questions->Miscellaneous, in particular the
calibre is not starting on Windows? and
calibre freezes/crashes occasionally? items.
BR