HTTP Error 500 on PS3 - 7.6.0 and above

[Firefds]

Since version 7.6.0, the PS3 is returning a "Media center error: an HTTP (500) error has occurred" for some files (a lot actually).
The playback of these files work perfectly on 7.5.0 with the same settings.

I've attached 2 logs:
One for 7.5.0 where the file plays correctly
ums_dbg-7.5.0.zip

One for 7.7.0 where the file and others don't play correctly
ums_dbg-7.7.0.zip

[Firefds]

The issue is with the subtitle settings.

As I need English subtitles for any program, I usually set the subtitles settings as *,eng
When I do that, I get the 500 error.
Other subtitles settings that don't work:

*,*
eng,eng

Basically, anything but the default eng,off;*,eng;*,und doesn't work.