Citizen,
I have just added new company on my existing FA installation using Arabic COA with standard login 'password'. To be sure nothing was overlooked, I have also installed Arabic language pack and set this as default. All works without problems, I can login, logout and work without problems, so I'm at least sure there is no bug suffering my example configuration i.e. MySQL 5.1.49-3, php 5.3.3-7 on Debian Squeeze.
Please try to do the installation as follows:
. Install FA from scratch in standard en_US configuration
. Install Arabic COA and lang pack
. Create new company using arabic COA and password 'password' and prefix suggested ('1_')
. Logout and try the new created company.
If you still have no access to new company with 'admin'/'password' credentials, dump database using some sql tool e.g. phpyadmin and send the file with comments to me, than I will check the content and try find the reason.
Janusz