Plugin and update error

Hi, I am getting the following error which is stopping me from upgrading to the next version of WP (3.04), updating any plugin, or adding any new plugin.
Here it is:

Could not create directory. /hermes/bosweb/web225/b2251/ipw.username/public_html/blog/wp-content/upgrade/wassup.tmp/wassup

This happens for every plugin/upgrade. Any patch for this?

Thanks!