I take it you have tried the obvious thing which is enure that the drive is set to master. It shouldn't make much differenct normally but then this case is not normal. DO NOT under any circumstance lowlevel format an IDE drive. They don't tend to work very well afterwards.
This drive sounds old. I hope you are using an Amiga 500 Power Supply as the standard Amiga 1200 PSU's were absoulte junk and didn't supply near enough power to run a 3.5 inch.
I owned an A1200 with an 040 and a A500 PSU. I bought a Maxtor 1Gb drive and it worked for like a week and then sudenly it stopped. No matter what I did I couldn't get the disk to show up on boot. Chuck it in a PC, format it and away she goes. I concluded ( although not with any real testing ) that the PSU wasnt supplying the watts to run it properly. Just because the disk spins up doesn't mean the drive is working.
You could steal a PC psu and power it externally. Although if you don't have one just laying about then this might be a waiste of time. But if you do, it could dispell the PSU issue quickly.
You might also consider that neither Amiga or Hitachi DK223A-11 comply 100% with the IDE standard. There were some LG CDROM's that had this problem and a kernel patch in linux caused these things to stop functioning. Although this was to do with ATAPI rather than IDE.
There are so many things to consider here. When you have done some more testing, let us all know how you went. Perhaps you will discover some more information which will spark some ideas
Cheers
