The Avidemux packages in the repositories aren't old but their version is 2.5.6, which means that there's a serious problem with them: the sound doesn't remain synchronized with the video. This can be corrected manually, but if you really want to get it right it's a very tedious process, snd it has to be repeated for every video file you edit.
The problem has been solved in the 2.6 versions.
I've been running 2.6.1 on a test system since January with no problems, and I compiled 2.6.3 a couple of weeks ago - again without any issues.
Compiling the application would be easy if one didn't have to locate and install scores of codecs and .devel files first. After that it really is
easy as the Avidemux people provide a shell script that does all the work.
So I've done a package request: http://www.pclinuxos.com/forum/index.php/topic,116258.msg991039.html#msg991039