[POSSIBLE FIX] Flashing red light - dead phone/inferior USB cables
Today I had my One X happily connected to my pc, just transferring some files over by USB. Then when I wanted to disconnect it, it showed a lot of 'not getting enough current to charge and operate at the same time' messages. Dismissed them all, though it was time to put it on the wall charger, seen it's critical battery status.
Once I disconnected the phone, it immediately powered off and would not come back to life again. It was, however, greeting me with a flashing red light while on the wall charger. No matter what I tried (bootloader, long hold power button, charge it for some time), it remained completely dead.
Now I did get some new micro usb cables from eBay. Very cheap ones. Now I think these are the culprit. Apparently, while in file transfer mode, these cables were unable to provide sufficient current, causing the phone to drain the battery completely. Once I wanted to charge it, it couldn't boot to charger mode due to the battery being completely empty.
Hooking up with the original HTC cable again, it still showed the red flashing light. Exact same behavior. Until I (for the heck of it) tried to bash the power button quickly. It suddenly came back to life again and started charging again through PC.
If you find yourself in the same situation with bad USB leads (something to do with resistance of the cable?) or a red blinking light, try tapping the power button quickly instead of trying to boot into recovery mode. It might save you a postal return and a week or 3.
Or your ass, if you rooted it before it stopped charging.