Mask Edit control does not display required pattern.

I used Masked Edit control from VB6 for date entering, the input mask was ##/##/##, it displayed as __/__/__. An application was installed on the client’s computers and worked fine. But at one computer it behaves strange, displayed only question mark: ‘?’ . The system date setting at that computer originally was in a different format from those computers where the application worked OK. But after the date settings have been changed, it still gave no result. The interesting thing, that another control on the sane form used pattern like “###-#####-###-##” (in string format) worked OK.

Anyone knows what caused the problem?