How can i lock an application on my samsung solstice?

I want to lock my messages and memos on my samsung solstice sgh-a887 but every time i try to do it by putting in a password it tells me: Incorrect Password. What can i do to fix this? Or how can i figure out what my password is? Thanks :)|||The usual password is usually the last 4 digits of the phone number. If that fails, try 0000, 1234, 9999. If it allows 6 digits, try 000000 and 123456.

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