I have had this same problem for years now. Depending on the computer I use, I either have to use task manager to close SWTOR, or the whole thing locks up and I have to power cycle the computer. One of the things I noticed is that I can usually tell when it's going to happen while playing the game. The action gets very laggy, to the point where I cannot contribute to group play. When I exit the game, this lock up happens. Memory leak? Not sure. I will try the file deletion mentioned here and let you know.