Hi,
Wrong ffmpeg version installed? I have Debian Wheezy in my ITX box, running ZM1.25 and working perfectly. The details:
Distributor ID: Debian
Description: Debian GNU/Linux 7.2 (wheezy)
Release: 7.2
Codename: wheezy
ffmpeg version 0.8.6-6:0.8.6-1, Copyright (c) 2000-2013 the Libav developers
built on Mar 24 2013 07:20:17 with gcc 4.7.2
*** THIS PROGRAM IS DEPRECATED ***
This program is only provided for compatibility and will be removed in a future release. Please use avconv instead.
ffmpeg 0.8.6-6:0.8.6-1
libavutil 51. 22. 1 / 51. 22. 1
libavcodec 53. 35. 0 / 53. 35. 0
libavformat 53. 21. 1 / 53. 21. 1
libavdevice 53. 2. 0 / 53. 2. 0
libavfilter 2. 15. 0 / 2. 15. 0
libswscale 2. 1. 0 / 2. 1. 0
libpostproc 52. 0. 0 / 52. 0. 0
Hope it helps,
PacoLM