4
You have to look at your permissions, unchecking read only won't solve the problem...
Rightclick the cache, templates_c and upload dir and click on the tab security --> this can have a comletely different name but i don't know your language.
There should be a account with the name "Internet Guest Account" if not you have to add it to the root dir of your XOOPS website. Select this name/account.
The Internet Guest Account always has a name like this: Internet Guest Account(YOURPCNAME|USR_YOURPCNAME)
The permissions for this account should include "write"