Scene darkens with subtitles

Re-encoded 700mb DIVX file, following all the instructions for inserting subtitle srt files and everything seemed to go smoothly.
Burned the Video TS file onto a DVD, but when it plays, every time a subtitle is displayed, the scene darkens.
This is so distracting that it makes the movie unwatchable.
What needs to be done to have only the subtitle display while the rest of the scene maintains the same brightness as the rest of the frames?

Does this happen on both PC and standalone DVD player?