Dafydd Hopkin reports: The specific problem I have is from mysqldump files. A long line ~250K chars for example, containing parts like this... (123,123,23),(23,34,45),(23,453,345)...(repeating) Doing a replace (with RegExp) of '),(' to '),\n(' (ie, to break each out into its own line) seems to hang it. Have waited half an hour and given up - annoyingly have to kill IDEA, which loses any other unsaved files. Running on ultra edit this op takes <1 second. Sample file that can be used to reproduce this problem is attached.