2.2" TFT Display going white (Voltage Issue)

I suspect I have a voltage supply problem on my design. When I run the board off an external power source and the voltage supplied is less than a certain point (5 to 6V on my VIn for my MEGA), everything looks to work fine on my TFT. That is until I fire up my GSM module and current draw becomes an issue in which case the design keeps resetting. If I then up my voltage supply, the TFT goes white. On the other hand, if I run the board off the USB port, some USB ports work fine but others give me a white screen. In trying to figure out what was going on, I discovered that my 3.3V supply to my display seems to be the problem.

I have a supplemental voltage supply on my board to boost the 5V capcity of my system. I dont however have anything on the 3.3V side because I assumed that the only devices using the 3.3V would be my TFT and the CD4050 HEX converter that interfaces to the TFT. When I measure the voltage on my 3.3V pin and I have the right supply voltages on the Arduino (IE - More than 7V on the VIN), my 3.3V pin is reading up at 3.6V The only things this pin is connected to is the VCC on my TFT and the VDD on my CD4050 converter. I am thinking that the CD4050 is leaking back into the Arduino board somehow because if I remove the board and check the 3.3V pin, its bang on 3.3V. I dont think the display is leaking back to the arduino because all pins on the display are operating at 3.3V and it has no higher supply. The CD4050 on the other hand, has the 5V pins coming from the arduino which are being converted down.

Has anyone had this before? Is there something more complicated I should be considering when putting the CD4050 and my 2.2" TFT in? Can they not share the 3.3V pin? Maybe a quick way to check it is to put a diode onto each input pin running from the MEGA to the CD4050?

I am assuming this over voltage is the reason the 2.2" TFT is going completely white and that it is not the noise issue. I checked the noise and I am getting about 0.1V noise factor so will be capping that one too.

Thanks again for anyone's advice here.

No one?

In my case display work but voltage at 3.3V arduino pin are about 4.2V!

Problem are discussed at http://forum.allaboutcircuits.com/threads/my-cd4050-is-leaking-voltage-user-error.104876/. I don't understand how input current flows through two opposite diodes, but I at voltmeter screen see 4.2V.

It is seems that resistor dividers at display inputs and one-transistor low to high level shifter at sdi->miso (or direct connection sdi->miso) are preferred.