Here's a weird one for your consideration
 

Via Tools | Attributes | ItemID exists in system attribute group.

However, in item attributes, it does not exist nor can I insert it as it does not appear on the drop down attribute list.

Go figure. Now what? I don't want to reset everything as my desktop is highly customized.

Thoughts/Comments/Suggestions?

tools- options - attributes -> check ItemID

It is checked. That's why I'm asking the question.

you didn't say that!

tools- options - attributes is not the same as Tools | Attributes |

OK, you're right. I didn't say that. So now what do you think ;-) Or have I stumped you?

if you DO have checked in Tools-Options-Attributes-ItemID, then dont know ... :-)

Aha! Tools } Options | Attributes.... stupid me. That fixed it... . Thanks.