I just did a change to NRRect's default constructor.
Prior to this it was leaving all of its members uninitialized, and valgrind found that some like this were being checked for 'empty'. So random behavior could have been seen.
I also did a fix under display, but that was an array index going below zero, but I think the loop would have exited anyway, so I don't expect that change to really affect the program.
I'm mainly concerned that some bugs might have been caused by 'new' NRRect variables being seen as non-empty and now they'll show up as empty.
BTW, these were the first two things I found by getting to run under Valgrind and seeing what was reported right off the bat. I'll probably try to actually explore the app a little more under valgrind, but I think these two were a good start.