>>I assume that the code (referencing This.Buttons.(This.Value).Caption) is in the click event of the option button group, rather than an individual button. About the only thing that I can think of is that the value of the group isn't initialized or is somewhere set to 0.
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>You are right, the code is in the click event. But I am not sure whether the value of the group is initialized or not. Because if used with only a form, and the optiongroup buttons in it.And no tables in the buffermode etc. It can work.
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>Why?
The buffermode shouldn't have anything to do with this. All I can do is to suggest that you try to track this down with the debugger. Perhaps assigning the value of the optiongroup to a local variable (ie: lnoptvalue = This.Value) and set a breakpoint whenever that variable changes.

hth,