openshot freezes while editing

I'm using openshot 1.4.3 in ubuntu 12.10.
I'm editing DV clips.
After doing any editing task ( move a clip, cut a clip etc etc) , openshot freezes when I try to preview the proyect.
I run openshot from a terminal to see what happens.
What happens is that when I move the cursor at timeline or press play to preview the proyect, in the terminal appear a lot of warning lines like this:
"[dv @ 0x755c2a0] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x961f2c0] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x962a440] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x3631a20] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x9621dc0] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x9624960] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x9623680] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x3911020] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x61184c0] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x3921b20] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x3b12420] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x391a760] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x60f9f40] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x39ee1e0] Estimating duration from bitrate, this may be inaccurate
[dv @ 0x3bb8f40] Estimating duration from bitrate, this may be inaccurate
....................................."
Openshot remains freeze until this lines finished.
Then I can continue editing.
¿what can I do to correct this?
It makes editing complcated and too slow....