Hi.
I just downloaded the new Perian 1.2.
... and ran into a first issue
On some large .mkv, when loading them with Quicktime Player X or 7, Perian disables the main video track, and I get a big white rectangle instead.
On Quicktime Player 7, I can still re-enable it (I have a Quicktime Pro license), but that is not very practical.
Uninstalling and re-installing Perian, trashing its preferences, toggling its "load external subtitles" option on or off, restarting the Mac, switching the Mac's language form French to English, does not seem to help.
These files played well with Perian 1.1.4 and Quicktime Player 7, except of course for their subtitles.
As a first analysis, this seems to happen with files with forced subtitles only. Unfortunately that is quite a lot of the movies I have in a .mkv form. Files without forced subtitles seem to work OK.