WD drives have software that comes on the drive that is incompatible with Mavericks.
The WD software that comes with the drive, that they want you to install on your mac, is also incompatible with Mavericks.
In some cases, the WD drives have firmware in the drive enclosure that is also incompatible with Mavericks.
All of this software is unnecessary in the first place.
If you just bought a WD drive, I'd take it back for a refund.
If your drive is one of those with the incompatible firmware, you could check the WD site to see if they have compatible firmware now. If you trust WD (I wouldn't). Another option is to remove the drive from the enclosure and put it in another (non-WD) enclosure, which is not too difficult, if you know how to use a screwdriver. Such enclosures can be found for a few bucks. I found one for five bucks in the bargain bin at Office Max.
Otherwise, you should backup any documents on the WD drive to another drive, and reformat (erase) it, and uninstall any WD utilities on your Mac.
If you like these drives, you can probably pick them up cheap now. I just saw another website with them on sale.