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Did this just happen out of the blue or is your Evo rooted and/or flashed to a custom ROM or completely stock? Have you tried to do a factory reset by:
Turn the power off. If your HTC EVO 4G is frozen, pull the battery out and reinsert it
Hold the Volume Down button
Press and release the Power button
You are now presented with a menu that allows for Fastbook, Recovery, Clear Storage, and Simlock
Select Clear Storage by pressing the Volume Down button
Press and release the Power button
Now simply confirm your decision: Volume Up for YES and Volume Down for NO
If you selected YES, all data including third-party applications will be deleted from the HTC EVO 4G. Once the wipe is complete, the phone will reboot to its factory fresh state
Also you may get a faster answer and help from fellow Evo 4g owners if you post this in the
HTC EVO 4G - Android Forums section since its more phone specific.