[Droid Incredible Q&A, Help & Troubleshooting] GMPOWER:
I have only run MIUI rom for about 2 hours, so I can't give you specifics on how or why this happened. I can only tell you what I would do to fix this problem. Since you were able to install MIUI rom I would say that you have install clockworkmod recovery.

1.	Pull the battery to get it to turn off and then boot into recovery, hold volume down and then press power to start the phone in recovery.

2.	Now you will be at a menu with three android figures on skateboards at the bottom of the screen, now use the volume down key move down to “RECOVERY” and then press the power button to to select it.

3.	Now you should be in the clockworksmod recovery, press volume up to move to “mounts and storage” and then press the track point to select it.

4.	Now that you have this menu open make sure your USB cable is plugged into the computer, now press the volume up to move to “mount USB storage” and press the track point to select it. Your SD card should now be mounted on your computer for you to transfer all of your files back to your card.

5.	At this point if you don’t have a known stable backup that was created by clockworks, I would go and download an almost stock rom such as Virtuous 3.2.0 http://xdaforums.com/showthread.php?t=765447 and transfer it to your card. When it is done transferring press the track point to select “Unmount.”

6.	Now you should be at the “Mount and unmount partitions” screen, press the power button to get you back first menu of clockworkmod recovery.

7.	If you have a working backup on your SD card that you want to flash, then press the volume up key to select “backup and restore” and select it with the track point. Now just press volume down to select “Restore,” now just press the volume down key to move down and select the image that you would like to restore.

8.	If you downloaded Virt. 3.2, then just press the volume down to select “wipe data/factory reset” and then after that is down press volume down and select “wipe cache partition, “ and then volume down to select “install zip from SD card.” At the “Apply update from .zip file on SD card” menu volume down and select “choose zip from SD card,” use the volume down to scroll down and select the Virt. 3.2 zip that you downloaded earlier. Let it go through with installing the zip and then select “ reboot system now.”

9.	At this point you should be back up and running with a clean phone, you just need to restore all of your data with whatever backup program you were using, or you need to download and reinstall everything.

If you would like to try your new SD card again, and still have a copy of all of the files on your computer, you need to turn off the phone and install the new SD card.

10.	Now just hold down the volume down key and press power, use volume down to scroll to recovery and press the power key.

11.	Now in recovery press volume up to scroll to “Mounts and storage” and select it with the track point.

12.	Now press volume up and scroll to “format sdcard” and select it with the track point.

13.	When it is done get back to the “Mount and unmount partitions” screen and press volume up to select “mount USB storage,” and transfer all files back to your new SD card.

14.	When you are done unmount and press the power key to get back to the main “Clockworkmod recovery” screen and select “reboot system now” with the track point.

15.	You should now have your new SD card on a working system, and the rest is up to you on what you want to do from there.

If you don’t have the SD card files on your computer then follow 1 – 4 with your old card in place, and the follow that with 12 – 15 after you change your card.

I hope you can follow this and get a working phone, just report back if you have problems or if this helped you.