00000031 Installation involves creating a scheduled task error

I am trying to push Sophos out to all my cleint Pcs but get the following error on about 20 % of them

00000031  Installation involves creating a scheduled task on the computer. This requires the default admin share (called C$) to be accessible.

I have checked they all have remote regsitry service running and can confirm all have the default c$ share. All these machines were running an old version of Sophos until very recenetly when I upgraded to Endpoint

Has anyone else experienced this problem

Thanks

Nat