This is kinda picky but as a professional it bugs me:
There are a number of  lines (in the .rtf) which appear as for example:

<Can`t set trimmode parameter - AudioStreamNumber>

where the character which is supposed to be an apostorphe <'> (after the <Can> and before the <t> is actually a grave accent character <`>.

Some other lines have the character correct, such as:

<Can't reopen video window. Playing stopped.>

Most lines do not end with punctuation (the most recently quoted does and the line quoted earlier does not). There should be a decision as to whether all lines should or should not be punctuated at the end (Lines that are questions must finish with a Question mark <?> Personally I like punctuation but in dialog boxes, etc. it is often superfluous.

Is <trimm list> a misspelling? I would expect <trim list>.

<config> should be spelt out <configure>, naturally when it is part of the running text and not when it is part of acommand name or the like (if there is enough room in the dialog)

There are a number of lines of the .rtf file with questionable English, such as :
Creating of SolveigMM AVI FileWriter has been failed

This should probably read:
Creation of SolveigMM AVI FileWriter has failed

And likewise for the other lines that follow that pattern.
I am in the process of translating the AVI_Trimmer into Swedish (though most swedes do know English...)