Bad picture with Ultimo DVB-C

Hello,

I have a problem with my picture quality on my Ultimo with two DVB-C tuners. I turn in OpenPli with latest updates. The image pixelated at times on the HD channels. The signal looks bad with a SNR 60% AGC 75% BER ~ = 1,640,000 on all chanels (HD and SD). I've tested a VTI 4.1 and i've the same problem. I plugged other boxes (Azbox Premium+, Dreambox DM 800) and I have no problem. The signal is exellent with a SNR 75% AGC 95% BER = 0 ! Maybe a driver problem ? What can I do or test to solve this problem ?

Thank you.

Best regard

(Sorry for my poor english)