[support] Private file transfer keeps enabling itself

Hi

I have a D6 site which has the private uploads module enabled and a slew of others. Every so often (like once/twice a week) i will find that the file system has changed my setting of 'Public - files are available using HTTP directly.' to 'Private - files are transferred by Drupal.'

I have to get to the bottom of this as each time the file transfer method is changed to private, all the IE clients start seeing white screens (too many css files) as css + js aggregation is turned off.

Does anyone know of any condition that would prompt this setting to change automatically? I have taken the step of disabling the private uploads module just in case this has anything to do with it.

any help appreciated. cheers.