Welcome to the forum.
Can you post a screen-cap of your Timeline showing the Clip(s) that you are attempting to play, with the CTI (Current Time Indicator w/ the red Edit Line) over the Clip and also the Program Monitor?
Also, when you Dbl-click one of the Clips in the Project Panel, does it play in the Source Monitor?
Knowing the details of the Clips would be useful too.
I can't preview in the Source Moniter when I double click on a clip either. And I've made 5 separate projects with multiple clips in the past couple weeks and none of the clips have been able to preview, so clip info doesn't really matter. I attched the printscreen of the workspace.\
printscreen sheri.doc 488.0 K
OK, you have Imported VOB, which mostly contain MPEG-2 AV files in the VOB container. Are all of your source files VOB's? Are these from a miniDVD camera? Which one, make/model? What is your Project Preset, and how did you Import the VOB's? Very likely something in there.
This ARTICLE will give you a bit more background on VOB's, and what they can contain.
Good luck, and thanks for the screen-cap, as it showed a lot.