AVI+SRT => MP4 , trouble with convertion

[GiPiKay]

Can somebody help me? I've tried eternally with this on Windows, and now that I'm on Ubuntu I'm trying once again.
My objective: an Mp4 video file, with embedded subtitles, with source files being AVI video, and SRT subtitles files.
(My system is on spanish language, so I'll try to make the translation of the interface as accurate as possible)
The problem:I'm using the Convert/Save options, then I choose the AVI file, marking the subtitle option, then I look for the subtitles files, then I press Convert/Save,on the next panel I check "File" then choose the location adding "name.typefile" (in this case Mp4), then i choose Encapsule Mp4, video codec Mp4 scale 0.25,bla bla bla...all the subtitles options,or choosing the preset for ipod,then "choose all elemental transmition", and finally save.
Even with some variations, as choosing the presets instead of manual settings on the last screen, I've always got the same error:
Fail at reading file:
VLC couldn't open file "location/video.avi :sub-file=location/video.srt :subsdec-align=0 :freetype-rel-fontsize=12".
Your entry couldn't open:
VLC is unable to open MRL 'location/video.avi :sub-file=location/video.srt :subsdec-align=0 :freetype-rel-fontsize=12'. See log for more details

Any ideas?
If you want I can post the error on spanish, or a step by step images, of what I do, but I need someone to point me on the right direction

[Jean-Baptiste Kempf]

DO it from command line.

[GiPiKay]

Do you have any template to do it?
As on my post with location/video.avi and location/video.srt, and with mp4 as target
EDIT: I've found that if I put the subtitles out of the equqtion, it simply works, with no errors, but my target is an mp4 with permanents subtitles,Any ideas