[Deceptor]

You need to specify your username and password for XCache, remember the password in php.ini should not be an actual password, but an md5 encrypted password, then you enter the plain-text password in the prompt. Otherwise you can disable the admin authentification for XCache, see a couple of posts above to see how.

As for vboptimise/, yes it should have read/write permissions, as specified in the Admin CP descriptions when you setup vB Optimise