Have you checked your safe_mode setting?
You could check it in your admin site.
Click the setup tab and then system information. You will be shown information about your server configuration. Search for safe_mode. If this setting is set to on, you will have problems in order to work with your cache files. You can also try to upload a simple php file to your server with <?phpinfo()?> in it and see what it tells.
Some shared hostings have this option enabled for security reasons, but there are many links over the internet telling about the problems of having this setting enabled
There is also some issues reported for EZ http://issues.ez.no/9662
Hope this helps.
You must be logged in to post messages in this topic!