Emergency iPhone Tech problem

Apple iPhone - Emergency iPhone Tech problem

for no reason at all my Phone button wont bring me to my Phone Dialing screen.
All other phone functions work, like mail, texting, etc. and I can even call someone if I Text them first then use the Call button from the text message screen.

But, Pushing the Green Phone Button makes a totally white screen then it bounces back to the main menu.

I tried Syncing, didn't fix it, I checked my memory usage, still have plenty left.

any ideas, or where would I find the answer to this, I need to use my phone out in the field all day on Wednesday.

iPhone Tutorial
Have you tried a restart? Press the top button until the slider appears. After it's shut down, press the top button again.

http://www.apple.com/support/iphone/assistant/phone/

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Have you rebooted the phone? (as in, power down, wait 30 seconds, power up)?

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Have you tried to reset your phone? Hold the home and lock buttons until the Apple logo appears on the screen.

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With a corrupted Apple app, I would think that it would require a Restore.

Make sure that you make a fresh back up first, and copy over things like your photos and other docs, that a sync or back up do not touch.