[horde] Authentication question

[DEVEL STAROSTA]

Hi all,

This is my first post, sorry for my english;)

I'm very entusiast of horde project (pretty, simple, great work). I've 
tryied to install on my Gentoo box directly from source aprox. 10 times 
but still have some problems:
- I want login with administrative privileges to add/modify users but 
with IMP auth can't do this
- If I switch to horde authentication I see screen:
   "horde does not provide an authenticate() method"

I can't understand how I can to login with administrative privileges in 
order to make all modifications & after login with unprivileged users to 
read mail, add appointments ecc.

With regards, Alberto