I recently dealt with some poorly generated XHTML files. The generating script forgot to insert any return, so the resulting files were only one row but with 1~5 million columns.
EmEditor bacame very slow when I tried to sort the file out, both in navigation and search and replace. I used the latest Emeditor 7.0.3.
In the end, I had to use Notepad++ to edit them. Everything worked fine in Notepad++ regarding these pathetic files. But I still like EmEditor better. So please look at this issue and see if you can replicate it! Thanks! :-x
Please email me that sample file after zipped to email@example.com if you really need that optimization. Each file has a different factor that slows the overall speed, so it is important to reproduce your situation here. Thanks!