Thank you for the screenshot, sbm1.

I've set up the same item under the Manufacturing Overhead account. Then, created a bill from the created purchase order. And, the transaction hits both the A/P and  MFG Overhead account. See the attached screenshots below for your visual guide.

If you made some changes to your item list, you can re-sort it to undo the order. Let me show you how:

1. Go to the Lists menu.
2. Click the Item button, then choose Re-sort List.
3. Choose OK.

You can run the verify and rebuild utilities to perform a well-data checkup. This will make sure the item is damage free. 

If the same issue persists, the item could be damage. I recommend deleting the bill and purchase order transaction. Then, make the item inactive and re-set up a new one.

Once done, enter again the purchase order and the bill. Then, check what accounts are affected.

Let me know how everything turns out by leaving a comment below. Just tag my name, and I'm always around to help.