The only thing i can add is that if I use the 'General Search' box without going into the 'Special Search' I generally do not have a problem. I can type in "title: "Any title" and it works like a special search but does not crash. If I go into 'Special Search' and type under Title 'Any Title" it will more often than not crash. It is affected by going into the 'Special Search' part of the program.
The only other difference that I might have to a lot of users is I have in excess of 10,000 books in the Calibre Library.