Phone vibrates 5 times and goes black, only fully boots while plugged into USB at splash screen

Question

I have an HTC Droid Incredible with stock firmware 2.2 and it will no longer boot properly. The phone is not rooted or altered in any way.
When the power button is pressed, the phone shows the HTC Incredible splash screen, vibrates 5 times, and the screen goes black and the LED light flashes green over and over until the battery is pulled out.
Strangely enough, if the phone is plugged into a PC via USB or a charger during that splash screen for a few seconds (at least 5), it DOES boot up to the OS and seemingly works fine, but the SD card and internal storage is listed as "unavailable".  I can also access the HBOOT menu by holding volume- while turning the phone on.
The phone then functions until the next time it needs to be rebooted, or if you attempt to plug it in via USB again (only when attached to a PC) and remove it, then it vibrates 5 times and goes black once again.  If you repeat the battery pull and USB plug-in process it works again.
I've been able to successfully return it to the factory setting, reflash the stock ROM via SD from the HBOOT menu and from a RUU from my PC, but it doesn't fix the issue. The SD card has been reformatted properly and error checked and can be accessed from a card reader... just not while it is in the phone.
Pretty weird issue that's driving me crazy.

Answer 1

This reply in that link is what I am suggesting should have been implemented in the Droid 4:
“Just adding my 2 cents.  Found this to be odd with my new phone.  Previous WM6.1 phone I would sync and charge overnight with my PC and let both 'sleep' when done.  WM6 must be closing the port when the USB power drops so not to deplete the battery.
Just one more quirk with the new device.”
There is no reason for current leakage into a sleeping computer because of keeping data lines open.  It should be easy enough to shut down the usb port when a voltage drop is detected in on the power pins.  In any case, hopefully my posting will at least alleviate some anxiety for someone down the line.  The procedure gets the phone back up and running in an expedient manner.  Thanks for your research.