Kils - you are having a lot of problems with software that works well off the shelf if you follow the install directions.
http://www.fengoffice.com/web/wiki/doku.php/installation:installationI would suggest you follow the instructions - they are a little old, in that they suggest Debian 6 (which I use still), and then install the required programs, modules and libraries.
You are also using version 2.6.1? Can you consider using the most recent 2.6.1.6, or trial 3.0beta (although you may want to wait for it to move to RC or full version as there are a few minor bugs in the beta version (however, we use it in a production environment with no major issue)
I would suggest that you start from the beginning, following the instructions as the sheer bulk of the issues, suggests that perhaps there is something wrong with your server configuration or the install.