dari hasil googling, akhirnya ketemu solusinya.

Masalah awal, muncul error :

Server Error in Application.

Required permissions cannot be acquired.

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Security.Policy.PolicyException: Required permissions cannot be acquired.

solusi :

By checking Stack Trace, the error means that Microsoft.Practices.ObjectBuilder assembly failed to be loaded, because CLR security policy was not going to grant that assembly what it had asked for in its minimum grant set. You need check its minimum request set (either by looking for .permissionset reqmin in ILDasm, or if it’s a v1.1 assembly by using PermView).

It looks like your application uses reflection which requires Full Trust.

<trust level=”Full” originUrl=”" />  ( in Web.config file)

Problem = solved… ready to rumble again…

untuk menginstall modul virtual host, download modulnya terlebih dahulu dari :

Virtual server (756 kb)

untuk menginstallnya, click -> Webmin Configuration -> Webmin Modules.

Setelah terinstall click -> Re-check and refresh configuration.
Untuk mulai menambahkan domain anda, click Create Virtual server

wget http://prdownloads.sourceforge.net/webadmin/webmin-1.400-1.noarch.rpm

(bisa diinstall di Redhat, Caldera, SuSE, Mandrake or MSC Linux, 13M)

kemudian untuk menginstallnya, login terlebih dahulu menggunakan root :

rpm -U webmin-1.400-1.noarch.rpm

Pastikan menggunakan huruf U (u besar) !

Installasi akan otomatis menggunakan direktory

/usr/libexec/webmin

untuk mengakses webmin anda gunakan link https://localhost:10000 dengan menggunakan username dan password root anda.

Username: root
Password: xxxx (password)

Instalasi hanya membutuhkan kurang lebih 2 menit… selanjutnya anda tinggal melakukan setting untuk domain dan visrtual hosting anda !