*Damn*Bad news. I tried many YT videos and several from other sites, but nothing Each video starts playing without any problem.
Anything I can do here to help gather more data? Debugversion/logging of the filters maybe? @tourettes ?
Additional logging would help, but there is just too many places (MPAR + source filter) that could go wrong so it is really hit and miss to try to find it. Current MPAR log looks ok, does the OV source filter log anything? Is there any differences in the log when the playback fails?