[Hidden-tech] drupal 7.9

[Kathy Puckett]

I need drupal advice. I tried to upgrade to drupal 7.9 and then I
couldn't upload photos on my forum.
Error message:  The directory sites/default/files exists but is not
writable and could not be made writable.
I reverted back to my former Drupal version from my backup but the
error message still persists.  I know it has to do with permissions
and have read direction to fix it on the drupal website but they are
beyond me.  Anyone ever experience this error and have a solution?
Thanks.
Kathy