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I have the unregistered Version 2.0.1, Build 2217 and a 1642 lines XML file loaded in one tab and a 2150 lines XML file in another tab. Scrolling and moving the cursor around, editing and just maybe every graphical change in the tab with the larger file is 2 to 3 times slower, feeling sluggish. It's easy to see that if you keep pressing the Right Arrow key, it moves faster in the slower file compared to the larger one. So I guess this is a graphical sybsystem problem.  Maybe the graphical buffer is too large for it to be changed at every edit in a snappy fashion.