K8055 and XP Embedded

Hi to all. I’m new to this forum and also to the K8055 product, so I need a little help.
I set up a project which uses two digital outputs of the K8055 card.
The entire project must run under Windows XP Embedded, in which we use a sort of kiosk mode.
The machine has 2 user: 1 with user privileges and 1 with administrator privileges. The one with admin privileges is for mainteinance purposes. Normally the app runs as limited user (with write/read permission when needed)
Unfortunately in user mode the K8055 doesn’t function. the OpenDevice command works well, but SetDigitalChannel doesn’t work (and no exception is raised).
I developed my app with C# and VS 2005 so I used the DllImport.
Does anyone know if I must give to the user some permission needed for the K8055D.dll?

Thanks in advance for your help