I found a way to get around the problem : it still blinks once but the text comes back.
It's not comfortable but at least you can read the subs.
Here is the way I do :
I use the free software
time adjuster
Also, I check the FPS of the video file (in my case 25)
I open the .str witch in my case was like this :
"
1
00:01:48,920 --> 00:01:51,639
(gråter)
"
and I convert it to mDVD format (specifying the 25 fps)
witch then looks like :
"
{2722}{2790}(gråter)
"
Then in BS player, I open the new subs as before.
Hope it helps