some time , My forum is happend like this :

i thought it was wrong user password but its not . i have tried with many user name . this thing still happend .

Is some thing wrong in the database . How to solve this problem . Plz help .

Just wait 15 minutes, Login Help

If you have access to the database (if it's your board) you can also
delete from strikes where username = 'you' to "reset" the count.

Or just:
But seeing as 15 minutes is long since up this is no longer needed.