Have yried disabling mod security on the server when editing the txt?

I wish I had more technical experience to help you but unfortunatly I don't.

I had a number of issues with plugins where I kept getting the same message as you and was advised on this forum to turn MOD SECURITY OFF

I initially asked my host to do this as I did not know how but they refused to do so and the problems continued until one day I noticed that the option to turn it off had been made available in the servers control pannell.

I turned it off manually and not had a problem since.

It's worth checking if they have applied certain rules to the mod security or if they have truned it off compleely. Bare in mind host's don't seem to like disabling it compleetly.