Adding another project as a clip doesn't work or results in "framed" clip

Having worked on a dozen small Kdenlive projects so far, I'm (still) having some issues, so I'm asking here for help. Maybe one or another issue may actually be a bug, but before filing bug issues, I want to make sure that the problem is not me in fact. For your information: I'm using the most recent kdenlive compilations from sunab's bleeding repository on a Kubuntu 12.04 installation.

Now for my problems:

1. I have one project A that is set to 720p as output and where the raw footage is 1080p. No problem so far. Now, I want to include project A in project B as a clip. Project B again is set to 720p. When I'm adding project A, kdenlive renders the "project" clip and when I drag it into the timeline I get the clip, but with a black frame surrounding it. I would assume that since both A and B are set to 720p, the clip should already be of correct size and completely fit the "viewport"?

2. From time to time, kdenlive renders the included clip A successfully but then displays just the broken clip image. Moving around the timeline the clip reappears, but when I try to render the project, it ends up with the broken clip image in the final output again. Any ideas of what I'm doing wrong here?

Any help greatly welcomed. And many thanks for the great work of Kdenlive!
-- TheDiveO