Wilson,
As you are finding out, the OCX version of thr MaskEdit is very unstable in managed code. I would recommend creating your own MaskEdit in .NET instead. Here is a link to an article that explains how to do this with code.
http://www.codeproject.com/cs/miscctrl/maskedcsedit.asp>How do i clear the Text of a MaskEdit Control?
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Cathi Gero, CPA
Prenia Software & Consulting Services
Microsoft C# / .NET MVP
Mere Mortals for .NET MVP
cgero@prenia.comwww.prenia.comWeblog: blogs.prenia.com/cathi