Hi there NateBeast,
That is really unpleasant.
As you were facing some issues with the drive, you shouldn't have stored your data back on it.
Most probably, the drive has failed. Yet, it will not hurt to attach the drive with different cables to another port. In many cases, I/O(input/output) error, could be caused by bad cables.
In case the issue persists and the drive appears as 4 GB(you can go to BIOS and see if it appears like that over there), then the drive has failed. I doubt that you will be able to retrieve the data, unless you contact a data recovery company. You can try some other data recovery tools though.
If the drive is under warranty, just RMA it, as the other guys said.
Apart from all this, you need to keep in mind that initialization, is a data destructive process.
Let me know in case you have some more questions,
D_Know_WD