idvd freezes on loading themes

What system are you running? What version of iDVD?

When did this begin? Did you run any updaters just prior to this happening? If so what were they?

As a first quick fix Boot into Safe Mode, Mac OS X: Starting up in Safe Mode, try from there. If successful reboot normally and tray again.

Follow this workflow to help assure the best qualty video DVD:

Once you have the project as you want it save it as a disk image via the File ➙ Save as Disk Image menu option. This will separate the encoding process from the burn process.

To check the encoding mount the disk image, launch DVD Player and play it. If it plays OK with DVD Player the encoding is good.

Then burn to disk with Disk Utility or Toast at the slowest speed available (2x-4x) to assure the best burn quality. Always use top quality media: Verbatim, Maxell or Taiyo Yuden DVD-R are the most recommended in these forums.

Control (right) - click on the iDVD application and select Get Info from the contextual menu. In the window that opens will be the version of the app.

What version of Yosemite are you running? Use the  ➙ About this Mac menu option to get the exact versionl

When did iDVD last work? Have you run any updaters since then?

Boot into Safe Mode, Mac OS X: Starting up in Safe Mode, and try from there.

I had the same problem. I'm running OS X El Capitan 10.11.5, but I had the problem on prior operating systems. I have found the answer, and I have to repeat this occasionally to overcome this issue. You need to run disk utility to repair the permissions. Disk utility has changed a bit over the course of many Mac Operating Systems, but here's what I do now. The procedure would be very similar in any prior operating system. Close out all programs and eject and disconnect any external drives (backup drives etc.). Open "Macintosh HD" from your desktop. Open the "Applications" Folder. Open the "Utilities" folder. Open "Disk Utility". Click on "First Aid" and click "Run". Prior versions may have had a "Repair Permissions" option which would be the correct option. It will take a couple minutes to complete the process. Once complete exit the program and reboot the computer. Open iDVD. This should solve the problem.