It all started with a new Asus VN279QLB monitor and its Displayport connector.
My 660Ti SC only worked nicely on the HDMI input of the new monitor but this i want to use for my PS.
On the DP connection all dark and black colors were totally washed out and much to bright.
I found that changing any setting in the Control Panel of the colors immediately made the colors
look correct even when not applying any of the changes. Unfortunately after a reboot or one time
3D mode and back all was wrong again. I tried several recent drivers and all did the same.
When reading around the net i am not alone with this but no real fix was offered.
Some suggest to change to YCbCR 444 but this doesn't work. When i try this it forces me to YCbCR 422
and i never can change it back to RGB. The setting with YCbCR 422 messes up the text also.
Others suggest to force over a tool the RGB full mode. They claim Nvidia falsely doesn't use this.
This makes the black color darker but totally messes up the white- and black-point.
Some others recognize that luckily also, so no fix here also.
Changing the JouJye DP cable to an Eizo didn't help. Because of other problems i had 3 of these Asus
monitors here and all did the same. All kind of Windows cleaning and reinstalls didn't help.
I decided to call EVGA support and we started a RMA.
When uninstalling my 660Ti i recognized the first time that my HD4000 integrated also has a Displayport
connector on my ASRock extreme6. This one does the right colors all the time!

The 660ti SC RMA "Re-certified" cr** arrived and looked ok but crashed immediately even on the first round on Heaven.
I had to lower the core clock by -76MHz to get it stable.
Also the brightness bug still was there :(
I now tried rolling back many driver revisions and voilá 314.22 was fine with the color! From 320.00 on ALL drivers behave wrong in the same way.
I Emailed driverfeedback@nvidia.com 2 times with explanation and a dispdiag data file but never got a response.
I am sure it is some problem that only appears in some combinations. Strangely enough people reporting this bug often use an Asus monitor DP.

Back to the RMA card. I was 2 weeks without gaming meanwhile and after complaining again my second RMA was
an upgrade to a vanilla 670 from EVGA being merciful for complications with my first RMA.
This one works. Its boost clock maxes out at 1032 and the maximum stable overclock is at whopping 1058MHz.
The other downside is that the first time i have problems with the graphics card interfering with my cable TV card.
Even with the signal at full strengh the signal quality gets low as soon as the GTX670 clocks higher. I therefore get stutters in TV
playback when the GC sometimes gets clocked higher while browsing the net. I may find a solution with placing it different in my
computer but for completeness i wanted to mention it.

It seems the RMA cards i received were buggy before and somehow managed to slip thru QC on the second try or are cards that barely made it.
For my 670 it may have been a failed QC card until a later Bios made it manage to pass just in spec.

Sorry for my long post that may have a sour note but i found this forum a good place for my rant :)

Try putting the video card in another system and see if it acts the same..

Now that i finaly decided to post my stuff here i tried it one more time.
Sorry if i am late with this but i really found a fix for the brightness bug.
On the 3d-Center.org forum someone gave the advice to disable "include extension block" with the help of "Custom Resolution Utility (CRU)"
I don't know what this option exatly does atm but it works perfectly for the colors. One downside may be for some that audio over DP is disabled then.
A short read over a very long CRU thread hints to a solution to get audio support back over a custom monitor.inf but this i don't know for sure yet.
 
Edit: with CRU you can create your own monitor.inf for further use and disable this extension block thing.
Edit_2: after Hibernation this setting doesn't stick. Please Nvidia fix this with your drivers or hardware so we don't have to fiddle around. Intel and AMD has this working out of the box!!
Edit_3: created with the help of CRU a monitor inf file that disables all EDID extensions but audio, so it still works with the right colors and audio. Somehow i can't enter a html textbox, so if interest please PM

Hello to California, nice someone of the green guys look bye! I checked the Emails and i did send my 2 prior ones on 5. of december and 3. of january to exactly this adress.
I now did send you the recent DispDiag log created with 334.67 beta still producing the same problems. I hope you will find a solution.
So long this inf avoids this problem for me:

Asus_VN279QLB_DP_CRU.inf
---------------------------------------------------
[Version]
Signature="$Windows NT$"
Class=Monitor
ClassGUID={4d36e96e-e325-11ce-bfc1-08002be10318}
Provider=%MFG%
DriverVer=01/22/2014, 1.0.0.3

[Manufacturer]
%MFR%=Monitor,NTx86,NTamd64

[Monitor.NTx86]
%MODEL%=Monitor.Install

[Monitor.NTamd64]
%MODEL%=Monitor.Install

[Monitor.Install]
DelReg=Monitor.DelReg

[Monitor.Install.HW]
DelReg=Monitor.DelReg
AddReg=Monitor.AddReg

[Monitor.DelReg]
HKR,EDID_OVERRIDE
HKR,MODES
HKR,,DPMS
HKR,,ICMProfile
HKR,,MaxResolution
HKR,,PreferredMode

[Monitor.AddReg]
HKR,EDID_OVERRIDE,"0",0x01,0x00,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0x00,0x04,0x69,0xA4,0x27,0x00,0x00,0x00,0x00,0x24,0x17,0x01,0x04,0xA5,0x3C,0x22,0x78,0x3A,0x2F,0xA5,0xA5,0x54,0x50,0x9E,0x27,0x10,0x50,0x54,0x2F,0xCF,0x00,0x81,0x80,0x81,0x40,0x95,0x00,0xA9,0x40,0xB3,0x00,0xD1,0xC0,0x01,0x01,0x01,0x01,0x02,0x3A,0x80,0x18,0x71,0x38,0x2D,0x40,0x58,0x2C,0x45,0x00,0xE0,0x0E,0x11,0x00,0x00,0x1E,0x00,0x00,0x00,0xFC,0x00,0x56,0x4E,0x32,0x37,0x39,0x0A,0x20,0x20,0x20,0x20,0x20,0x20,0x20,0x00,0x00,0x00,0x10,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x10,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x01,0xA0
HKR,EDID_OVERRIDE,"1",0x01,0x02,0x03,0x0C,0x40,0x23,0x09,0x07,0x07,0x83,0x01,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0xF1

[Strings]
MFG=CRU
MFR="ASUS"
MODEL="Asus VN279QLB DP (EDID Override)"
VENDOR="Asus"

---------------------------------------------------

Cheers!

Thanks Manuel!