Child theme problem

Hi all!

I followed some instructions here on how to create a child theme. I followed them and all worked well.

However, after activating my child theme i get the following error:
“Cannot write cache folder. You may try setting the folder cache folder permission to 755 or 777 to solved this”

I have set the permissions and it hasn’t made the error go away.
The child theme is working ok, so should i be concerned?

This is the first time i have created a child theme so sorry if i have made a noobish error!

Thanks