I'm new to Cities XL - just got 2011. For the most part I love it, but this issue - whether it's a memory leak or a core problem or whatever - makes the game descend into unplayability for me after a while. My computer should be able to handle the game fine, but when I start getting 5-10 second lags on anything I do and it hiccups a lot, I find it too frustrating to play. I can restart the game and have it work fine for a while before the issue crops up again.