I have a 126MB text file of mostly short lines. I load it in EmEditor 7.00.1, hit Ctrl+A, and then hit Del to delete the text. The program crashes.
It sounds that there is not enough space for the Undo buffer. You might want to make sure you have enough disk space for swapping file or temporary files in your primary drive. I will try to reproduce your issue when I have a time. Thanks!