whmcs and virtualmin

Hi,
I have configured whmcs to use virtualmin server like instructed here: http://docs.whmcs.com/Virtualmin_Pro

However I always get “Module Command Error Server Login Invalid” when tying to create a virtual server in whmcs.

On virtualmin module debug I get this:

Unauthorized

Unauthorized

A password is required to access this web server. Please try again.

And this is what the target server logs tell me:

webmin[301]: Invalid login as root from xxx.xx.xxx.xxx

WHMCS seems to comunicate with virtualmin server but I always get an invalid login.

I need some lights please.

Thanks.