1) A faulty or inadequate power supply. Try another plug (preferably on a different line) and/or a different PSU or computer. Some drives are extremely sensitive (e.g. PX-716 which will flash an error code if it doesn't like you PSU).
2) A faulty IDE cable. Try a different cable, preferably the flat type, and make sure it does not exceed the maximum length of 45cm. Also check that the Master/Slave configuration is correct (remember Cable Select will only work with an 80-conductor cable).
3) Incompatibility between the drive and the controller. Are you using separate IDE controller card (make & model?) or a 3rd party controller on the motherboard (ditto). Are you using an IDE-SATA bridge?
4) Conflict/incompatibility with another drive on the same IDE channel (or even the other channel on the controller).
5) A faulty drive. Read/write problems may be caused by contamination on the lens, but the LED flashing could be an error code (search for a list of Yamaha LED error codes?).