Secondary Color Correction Doesn't Work

Hi. I'm using Premiere Pro CS5 on a new Macbook Pro with a Thunderbolt Display. Everything is working great except Secondary Color Correction. Using RGB Color Corrector (or 3-Way) I set the Output to Mask. The screen goes white. I select the Secondary Color Control eyedropper but the image stays white! I.e. I can't see the image to make a selection. And if I select blindly, the whole mask turns black. I've tried it without the Thunderbolt display, but its the same. Is this a software glitch or am I overlooking something? Thanks.

I think that was fixed in 5.5.2.

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Adobe Certified Expert Premiere Pro
Adobe Community Professional

I upgraded to 5.0.4 and the problem persists. The Adobe post (above) says its related to monitor settings but I get it even with a single monitor. Seems like a known bug. Oh well.