Chapter thumbnail stills, iDVD 7

Question

I am trying to create thumbnails in iDVD 7 for the Scene tabs.
Chapter markers were created from FCE export as QT with Chapter markers
iDVD 7 themes "Modern"
Sometimes this works, some times it does nto and I can not work out why
I have initially the 'tree' view ' selected.
I choose the slide that has the Scenes, and click on the thumbnail
Clicking it again, brings up a Small Info pane with a slider and a tick box for the "Still Image"
BUT this is where it often goes wrong.  Sometimes I can use the scroll bar to select the image I need..but very often it only alows me to select a thumb from the first chapter only ?
Sometimes I can select from teh correct chapter..but often, it won't work.
OK, so it is possible to go back to FCE and export individual slides for this, but it sems a long way to do it when there is a way built in to iDVD that works some of the time.

Answer 1

Create a new project, add the same movie and check to see if you can set the frame for each chapter successfully there.  If you can then you may have to stick with the new project. 
However, you can try this  basic troubleshooting fix:
1 - delete the IDVD preference file, com.apple.iDVD.plist, that resides in your
User/Home/Library/ Preferences folder.
2 - delete IDVD'S cache file, Cache.db, that is located in your
User/Home/Library/Caches/com.apple.iDVD folder. 
3 - launch IDVD and try again.
NOTE: In Lion and Mountain Lion the Home/Library folder is now invisible. To make it permanently visible enter the following in the Terminal application window: chflags nohidden ~/Library and press the Return key - 10.7: Un-hide the User Library folder.
If you're running Mavericks, 10.9,  go to your Home folder and use the View ➙ Show View Options menu to bring the this window:
OT