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yogi62 - try starting calibre with no plugins see
calibre command
Do you have a device attached - if so try un-attaching it.
Do you have any columns built from other columns that involve interrogating the database or file system serially. I recall a v.slow startup issue with displaying the virtual library names in the book list - but why one machine and not the other
How do you synchronise the copies of the library on two machines?
BR