HDMI black screen after startup (1 Viewer)

[DaFixer]

MediaPortal Version: 2.3.2
Windows Version: XP sp2
CPU Type: AMD64
Motherboard: ASUS

Hi have some problems with my hdmi port on my hdmi add-on card.
I get picture when my media center startup, but it's stops after the "Welcome"screen.
and when the screen is black i can hear sounds from MP.

And i buyed a dvi > hdni conveter from ebay, Sometimes i get picture and sometimes i get black screen.

VGA cabkle works fine

yes finaly i fixed

i just installed ATI calalyst 8.1 and now its works fine

 

[DaFixer]

Not fixed at al . The HDMI works fine but when i want play mp3 on MP. The screen freeze and the music still plays

I just install ATI calalyst 7.2 and a bios upgrade and now it works.
Not my HDMI add-on card but my dvi=>hdmi conveter