Subtitles do not appear in simulate even if I click on subtitles display box

Please help...with your experience and genius brain. I'm panicking for this...

Subtitles suddenly stop appearing in simulator after I changed the text in the menu. (It was working fine till the point.) I thought I might have clicked on something accidently, so I opened up old file, but it's doing the same thing. Since then, any other projects have the same problem.

I clicked on "Force display" and clicked on "Apply to stream." Subtitles appear correctly in timeline as I play the feature. However, if I play it in simulator, subtitles don't show up (The subtitles display box is also checked). It's crazy to see it working fine in timeline but it doesn't in simulator!

I restarted the computer. Subtitles still don't appear in simulate. When I burned a DVD, of course subtitles don't appear.

Is this a bug of DVD Studio pro that was hidden and suddenly triggered? Or is there a secret button or setting I accidently changed?

I use DVD Studio Pro 4 Version 4.2.1
I use 2X2.66 GHz Dual-Core Intel Xeon with Memory 5 GB 667 MHz DDR2 FB-DIMM

Please help this hopeless girl. Thank you so much in advance...