>>I'm not sure about anyone else, but I've run into this bug before. Where controls will disappear from the designer window, but still be in the code, and still be in the HTML. The only way I've found to fix it, is remove the label from the HTML and Code, and drop another one and name it the same thing.
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>I removed it from the code and when I try to add it, I have an invalid property error as a reference still exists somewhere.

Check in the code behind, and make sure it is removed the Designer written code, I think the region is called Designer Generated Code, or something like that, and remove it from the HTML source in the ASPX file as well.

It is a pain in the butt, but I haven't found the reason why or a workaround why the controls do that.

Morgan