I've seen a lot of posts on this but no fixes. I just moved up to 2010a from 2007b (32 bit Windows XP) and took a massive editor performance hit. It seems to get worse as the size of the .m file increases. It also seems to get better if I kill Matlab and re-start. I have one .m file at about 7000 lines and it's very noticeable there. Minor improvement if I shut off the code checking but that doesn't seem to be the whole story. Any help is appreciated.