Problem nr.1:
I don't know if this is normal in digital tv, but sometimes (approximately every 5 to 15 minutes) video freezes for about 1 second. Signal level and quality are excelent. No matter which channel I watch, what decoders I use, what renderer I choose, it doesn't change anything. I have tried every available setting with no luck. If nobody is able to help, at least tell me WHY does this happen. Is this a software, hardware problem or it depends on the data stream broadcast? It's been about half a year I haven't found the solution to this problem...

Problem nr.2:
Sometimes when I switch to encrypted channel, no video or audio shows up, just a black screen and I have to close progdvb and open it again, because reswitching the channel or changing to another doesn't help. I'm using original conax module.

Both symptoms are NOT normal.

And there's no general reason nor solution.

You may have a to small amount of free RAM. This may lead to excessive use of the swap file, which is far slower than physical memory. Also think about reducing timeshift buffer, if located in RAM. If working on file, you may want to add a second physical HDD, place it there on, to avoid performance issues with the system disk. A second partition on the same physical disk won't help a bit. Perhaps use FAT32 on the second disk, in case use some extra tool for this. Performs better on most systems.

Or you may have some networking trouble, as DVB cards do behave like a virtual network card, to allow streaming out DVB audio, video and system data to the system / applications.

And in some cases, you may need DVB related updates for Windows, that don't always come from Windows Update automatically.

You may want to set the ECM used as default in channel properties.