I spent most of today editing MIDI. And had the same problem as the OP. It got to be very frustrating to say the least!
Just as he experienced, it would often take several attempts to lasso a group of notes w/o the Properties box appearing. I'd try lassoing a thin box (everything the box touches should activate) and it didn't work. Try to lasso large areas, like most of the notes within the box, and still get properties dialogue. Over and over until it 'stuck' and I could edit as I wanted.
Didn't try to pin down the problem and find a solution today as I didn't have the time to stop what I was doing. I'll have more time in the next few days to research.
Just reinforcing what the OP reported. Left-click, hold and lasso is not working as intended for me.