Probably it wasn't fixed. I installed (clean) MP 1.2.1, replaced IPTV filter and scan. After scanning wasn't created 'All Channels' group in 'Radio Channels' section. I run MP and as I wrote in first post, when I try to show TV channels (TV -> Channel), MP freezes. But solution is very, very simple. I created 'All Channels' group manually in TV-Server Configuration and everything works.This issue should be fixed in MP 1.2.1.
[Edit: Georgius, I recommend that you post a new bug report for the DVB-IP issue as I don't think that part of the fix was included.]