RoundCube - connection to storage failed.

Hi All,

I have spent a lot of time reading posts and different websites trying to get Roundcube to work with no luck.
There many threads and posts out there which I have tried, the only install guide that works to the point of successful (web installer tests) results on the web installer is official install instructions below -:

http://trac.roundcube.net/wiki/Howto_Install

After following the guidelines i still cannot log into Roundcube keep getting 'unable to connect to storage'
The sql database roundcube and usercube user are created and privileges set, so i'm unsure what is causing this issue when the installer webpage gives me green results on my set-up.

setup installed
Ubuntu Server with KUbuntu desktop. 12.04.2 LTS & 4.8.5 KDE
Roundcubemail 0.9.2
Postfix (and postfix admin) email working well.
Courier IMAP
SpamAsssassin, ClamAV, Postgrey, Amavisd
MySQL
PHP
Apache

Any advise or help would be most appreciated..