Hi. I'm getting problems trying to dissolve from one video track to another. The dissolve appears to work, but after the dissolve, it typically flicks back to the previous video for one frame.

I have tried changing the position of the dissolve to a variety of places (one frame ahead/behind at the start/end of the dissolve), but it is still flickering every time. Any ideas why?

Is this a bug? I'm wondering if the dissolve interpolation variable is wrapping around (eg. 0 -> 1, then somehow it's briefly 0 again?)

Is this occurring with h.264 encoded clips?

No. The original was an OGG file, as generated by gtk-recordmydesktop. mplayer -identify gives me this:

ID_DEMUXER=lavfpref
ID_VIDEO_FORMAT=theo
ID_VIDEO_BITRATE=0
ID_VIDEO_WIDTH=1280
ID_VIDEO_HEIGHT=720
ID_VIDEO_FPS=30.000
ID_VIDEO_ASPECT=1.7778
ID_AUDIO_FORMAT=22127
ID_AUDIO_BITRATE=499816
ID_AUDIO_RATE=44100
ID_AUDIO_NCH=2

Then I was having trouble editing it accurately, so I tried to convert it into a lossless Matrovska from the context menu, yielding this:

ID_CLIP_INFO_NAME0=ENCODER
ID_CLIP_INFO_VALUE0=Lavf53.21.0
ID_CLIP_INFO_N=1
ID_DEMUXER=lavfpref
ID_VIDEO_FORMAT=HFYU
ID_VIDEO_BITRATE=0
ID_VIDEO_WIDTH=1280
ID_VIDEO_HEIGHT=720
ID_VIDEO_FPS=29.917
ID_VIDEO_ASPECT=1.7778
ID_AUDIO_FORMAT=61868
ID_AUDIO_BITRATE=0
ID_AUDIO_RATE=44100
ID_AUDIO_NCH=2

Then it was basically editing that. In the end, I encoded to an avi using xvid, but the problem was in the editor as well as the final export.

I've also had this problem when using interlaced MTS (AVCHD) clips in the past.

Note that I mentioned an issue about h.264 in this thread: http://kdenlive.org/forum/oh-those-extra-frames#comment-18434

I had not encountered it yet with theora/ogg. I normally only use ogg audio for narrating/voice over.
You could have a look at your clips to see whether ffmeg and melt give different frame lengths.