It has been a long time since your post, but the bug persists. So I decided to write a bit of a rant, and give a hack for the problem above.
I have just bought a Humax HDR 1100S and subtitles have been my first source of frustration, they work terribly in this box. I am talking about trying to play some file video.mp4, video.avi, etc, with an associated subtitle file video.srt (whether in a USB key or in the internal HDD).
The Humax box is very finicky. The subtitle will be completely ignored if it is not encoded in ASCII (UTF-7) or UTF-8 with Unix end of lines (i.e. LF, and not CR-LF as in Windows/DOS or CR as in old Mac). Moreover the file must *not* have a BOM (byte order marker). On the other hand the Humax accepts many subtitle formats such as SRT, SUB (MicroDVD), ASS, SSA. But HTML tags in the subtitle (<i>, <b>, etc) will be ignored and will be displayed raw.
Problem is, when you have sorted out the above, only the FIRST LINE of every subtitle gets displayed. My hack/solution is to add an extra line to two-line subtitles, containing a single character such as "*" (the character does not matter, but the line must not be empty). Then, both the first and second lines will be displayed (and the third line with "*" will be ignored).
1) Too large gap between the 1st and 2nd line.
2) The hack only works for two lines, with three lines only the first two show up even if you add a fourth line with "*".
3) Yet another bug: if the first line is longer that 32 characters, it will still display, but annoyingly, the excess characters (i.e., all characters in the first line after the 32th) will be repeated between the first and second line! The second line experiences no issues, it can be longer than 32 characters.
Note: because of the bug above (i.e. third issue), try to only add an extra line with "*" when you need to display 2 lines. Longer than 32 character single lines work fine, so do not add a second line with "*" in these cases or you'll experience the third issue in its whole "glory".
Personally, all the processing above to get the subtitles (more or less) working I do with Emacs in Linux (using regex expressions, if you know what they are), but this will be extremely hacky for many people.
Come on Humax, these subtitle shenanigans we are subjected too are not good enough. We want a software update to fix all this stuff. Do take a leaf out of Samsung's book (a South Korean company too): my 7-year old Samsung TV can take any pair of video and subtitles files and play them no problem. No fuss with encoding, HTML tags taken into account, etc.
Subtitles should "just work", as in any Linux box (VLC, totem, etc). After all, Humax is using lots of GNU software, how could you get that wrong?
Fogar de Breogam