wincc flexible dh485 failed

Hello. I am trying to connect wincc flexible 2008 to AB slc 5/03 via rs232 with the protocol dh485. But when i run the project i got the message "failed to install fwDH485" and then "failed to start fwDH485, please install fwDH485"
I tried to install it manually but the device manager says that is updated.
Also at control panel in the SIMATIC HMI DH485 i can't select the option Use DH485.

I would like some help!!!!

What panel exactly ?

At pc.

Depending on the OS (from Vista and up), you may have to be logged on as administrator to install or change the driver.

If the above doesnt fix the problem, then try to remove the driver completely; follow this guide:
http://support.automation.siemens.com/WW/view/en/27149229

The reinstall the driver and try again.

I have tried it, didn't work.