Merging .srt Greek subtitles with .mkv

[wolfmandim]

I have been watching .mkv movies with external .srt Greek subtitles successfully so far. Lately, I tried to permanently add those subtitles to the .mkv using the MKVtoolnix 4.2.0 merger. The subtitles will show fine during playback, however, with a slight problem. Some letters from the beginning of every phrase are cropped. Need to know:
1. Am I doing something wrong? Am I missing something during muxing?
2. Should I use some other software to add the subtitles (please name free software)?

Thanks a lot!!

[wolfmandim]

I forgot to mention that I am using the latest version of BSplayer pro. I tried Windows media player and the subtitles will show problem free. It looks I will have to post to BSplayer forum to see what causes the trouble..
Thanks for the hosting!