Hot key on button won't show underline on character

[Rx_]

The attached image shows the run-time and the design-time issue.
While other forms have these exact two buttons and work perfectlly, this one is just stubborn and won't listen to binary instructions.

Any suggestions on how to correct this way-ward command button?

The yellow box is just a colored rectangle behind the Comments button.
This is on all my working forms as well.
If a comment exist for this form, the rectangle is green, if no comment exist it stays yellow. Just added that because someone might ask.

It is the parent that holds a tabbed subform. None of the other controls use the o . Even tried to use the &M and &T - exactly same results. Shows in Design time - but not in run time.

Nobody was rushing to suggest anything, so here is a little more:
A Main form opens one of about 8 forms - two work, the rest don't.

 

[missinglinq]

Only thing I can think of is that the button control has become corrupt. Have you tried simply deleting it then re-creating it?

 

[Rx_]

I think your right. I had another control on the same form where the change event just would not fire at all. Deleted it, replaced it and it worked fine.

Access 2007 with all the service packs running on XP. Honestly don't know if this problem is the customer's workstation, a network drive with high latency, or soemthing else. This has been a random problem off and on that manifest itself in different ways.

The data base was converted from 2000 to 2007. And later, all objects were imported into a new database.