Having the same problems as dnmpc & b.michelsen. Takes a while for anything to take affect, especially color changes. Only way some modifications work is to save the file then re-open. Can even take a very long time to load a .ttr file. Most times even clicking elsewhere does not help. Has never been quick for me but does vary between slow and very slow. My system is updated & all of the recommended items previously mentioned exist, .NET is current, font cache=disabled... Running TT 18.104.22.16846, Win 7 Ultimate. I have no problem running other programs such as Publisher, Gimp & InkScape that are highly graphic intensive. I've even turned off all cloud syncing, stopped any unnecessary background apps. It takes twice as long to do anything because of how slow it is. Would be terrific if it weren't so lagging, it's very frustrating.