Ronaldo, Im glad you found the workflow I suggested addresses the issue.
To tell you the truth, ever since I switched to the PC I have been avoiding using QuickTime as much as possible. There is the gamma problem you experienced as well as a slowdown when exporting from PrP due to the need for qt32server which acts as a bottleneck in the process, since Quicktime is not a 64 bit app yet. I dont see Apple giving a needed update any time soon.
I do use DNxHD for professional work. But Ive also started using MXF OP1a AVC-I 100 for mastering. It exports 2x as fast as QuickTime and there are no gamma issues.
I also switched to using the MP4 version of H.264 which also exports quickly and has no gamma issues.
Tom Daigon
PrP / After Effects Editor
http://www.hdshotsandcuts.com
https://www.youtube.com/watch?v=DxPrG3WUyz8
(Best viewed at 1080P and full screen)
HP Z820 Dual 2687
64GB ram
Dulce DQg2 16TB raid