The problem was (and still is) that ASL seems to recreate the .conf file every time it updates the rules !
I've added mod_security to the list of modules Litespeed shouldn't load and it seems to have done the job.
I'm now trying to find out why Litespeed is slower than Apache with FCGID… shouldn't it be faster ?
I'll open a new topic when I'm sure that nothing else is slowing things down.
I don't know why but your forum keeps cutting of the end of my messages and I have to click on return to copy the text then on edit to replace with the full text !