No video in ProgDVB's window, but recording works

#1
Hi, since some weeks I have this weird problem: no video appears in ProgDVB's window, just the name of the channel.

Another weird thing is that, when a new version of ProgDVB is out, after installing it the video works again... but then, the next day, it does not work again...

Finally, if I schedule a record, it records on disk with no problems...

I have:

Intel i3770
Windows 8.1 64Bit
32 GB of RAM
Radeon HD7950
TerraTec Cinergy T Stick RC (Rev.3)

Any tip on this, please?