Subtitle filenames format (1 Viewer)

[z3us]

Hi.
If I try to play a video named:
wall-e.avi

with external players (bsplayer, vlc,...), these subtitles are recognized:
wall-e.srt
wall-e [dual].srt
wall-e -spanish-.srt
etc

But, with MP only
wall-e.srt
is recognized

Why?

Im using ffdshow and vobsub as post-processing, following this guide:
MEDIAPORTAL - free media center - simple mediaportal codec guide

Thanks