Can you try the above example?
<CuteWebUI:Uploader runat="server" ID="Uploader1" InsertText="Upload (Max 100K)" MaxFilesLimit="2">
<VALIDATEOPTION AllowedFileExtensions="jpeg,jpg,gif,png" MaxSizeKB="100" />
</CuteWebUI:Uploader>
Here is the code of the above example.
It works fine for me.
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