Acrobat Reader - Loong delay on exiting

When I view a PDF file, it opens properly. But when I try to exit, it
takes almost a minute to close!

During that time, IE is frozen. The rest of the PC works OK but IE won't
refresh or respond to clicks.

I've tried uninstalling and reinstalling the reader to no avail.

After a fresh install, when I tried to close the PDF, I got a dialog saying
that one or more PDF files were open and closing Acrobat would close these
files. I clicked on the Don't show me this message again checkbox.

I no longer get the dialog but still have the long delay.

This is IE6 and Acrobat Reader 6.

Any ideas?

Thanks, Frank