MKV re-encoding^ No Video, only sound

[Windem]

Hi!
I encounter one annoying problem in Avidemux 2.6.1 x64 for Windows.
When trying to make 1.45 GB MKV file from 2.18 GB MKV file, Avidemux can't do that with mkvdemux (The former and the latter codec is H.264, Audio - Copy)- I get only sound and no video. In avidemux muxing mode it does NOT happen. The mode of re-compression (Constant bitrate, average bitare, etc) won't make a difference.
Any ideas?

[mean]

Try with that one
http://fixounet.free.fr/2.6/avidemux_2.6.3_r8649_win32.exe

[Windem]

Not a stable version - did not load 2 of my MKV files. Not to mention that it's 32 bit.
Thanks anyway. I switched to 2.5 as was posted elsewhere and it seems to work, excluding audio delay.