SQL 2008 R2 Setup problem

Hi,

I am in the process of installing SQL 2008 R2 on a cluster. The install gets to a point where I am presented with the Instance configuration. I fill in the details required and click next and get the following message "Instance directory (or command line option /INSTANCEDIR) value for a cluster installation cannot be a directory on shared drive". I have tried numerous configurations with the disk bu just can't get beyond this point

Thanks