webadmin login fail

[paskinel68 at gmail.com]

Hi all,

I installed a fresh kolab3 server on a debian wheezy, apparently it's 
all ok, but when i log in webadmin I receive a "internal system error" 
alert.
On the log of kolab-webadmin i found:

  PHP Error: Login failed. Unable to decode response (POST)

I try to connect on LDAP with Apache Directory Studio from a client and 
the directory manager credential are ok.

Any suggestion are welcome