[Ulrik Brask]

It turns out that I just needed to update the Colorista Fxplug-in on my system to the latest version. That one has no conflict with the drawing of Master Templates in the viewer.

[Ulrik Brask]

The problem has been solved now! Removing the Magic Bullet Colorita FXplug-in did the trick.
I deleted the MBCC.fxplug and the MBCC_Slider.fxplug form the ~/Library/Plug-Ins/FxPlug folder and the GLCapsInfo.framework from the ~/Library/Frameworks folder and now the Master Templates renders in the Final Cut Pro viewer again.

So be aware : The Magic Bullet Colorista plug-in from Red Giant Software has a conflict with the Master Templates in Final Cut Pro 7.

[Ulrik Brask]

I am having the same problem on my system.
All Master Templates looks blank (white) in Final Cut Pro 7.
I usually have two monitors connected but disconnecting one of them has no effect on the problem.
The Master Templates will load when selected from the viewers generator pop-up,

and the control-tab will be displayed in the viewer, showing all the proper controls for the selected template.

But once I select the video tab in the viewer, all I get is a blank white image. Editing the template to the timeline changes nothing, nor dose rendering the sequence.

Opening the same template in Motion 4 works fine. The problem only exist within Final Cut Pro 7 and only concerns Master Templates. Ordinary motion projects works without problems in Final Cut Pro 7.
Final Cut Studio 3 was installed as an upgrade on top of an otherwise fully updated Final Cut Studio 2. The OS is updated to ver. 10.5.8, the hardware is a MacPro 2×3.0 GHz Quad-Core Intel Xeon, 8 Gb RAM, ATI Radeon X1900 XT graphics card.

Any suggestions as to how this failure can be fixed would be most welcome.