Opus suddenly running bog slow

Two days ago Opus turned to sludge. I'm used to it being very fast, loading almost instantly. Now it takes minutes. Windows Explorer runs much faster, with no problems
I am running Win 7, 64 bit. It has been very stable.
How can I troubleshoot this problem? Re-installing Opus had no effect.

Can you be more specific about what's slow? Is it just startup time?