My setup: kdenlive 0.9.3+git from sunab's svn repository+mlt+libav
Kubuntu 12.04 64bit
Rendering of a clip is aborted using the H264 codec:
[libx264 @ 0x7f49589ae9e0] [Eval @ 0x7f495dffb490] Invalid chars '.6' at the end of expression '0.6' [libx264 @ 0x7f49589ae9e0] Unable to parse option value "0.6"
Happens only a single project that I recently changed from 720p/25Hz to 1080p/25Hz. Checking the transitions I could not find any problem indication.