Gentlemen,
I find very similar behavior to what you describe. I have been able to isolate it to times when I have resized the query window, or re-sized the query/data window split. The probability of a crash seems to be proportional to the number of rows of data contained in the data grid. If I resize my query window at the outset of my work - then never resize it - I am able to run for numerous days, or even weeks, without error. I am running the 1.20.0 (Dec 19 2014, rev: REL-1_2-_0) version.