Stuttering 720p MKV video with subtitles

[blwarburton]

When playing 3Mbps 720p MKV files with either internal or external SRT subtitles enabled the video is stuttered.
This problem started with VLC 1.0.0 and is still present with VLC 1.0.1.
If the subtitles are switched off the problem goes away.
MPC-HC and ffdshow 3054 plays the MKV ok. The problem can be replicated on all MKV files with subtitles.