screen lock problem

[dha_nhie_kha]

i got my xperia miro.. i love it but unfortunately i'm having a problem with its screen lock.. when i set it, i locked my phone so i may check and it's working.. but afterwards eventhough how many times i lock it, the security lock was not there, in short whoever wants to see what is inside may do it..what is the best thing i could do?? thank you

[Uliwooly]

have you disable any app? do you have a different home launcher and/or lock screen app? any taskillers/task managers? antivirus? battery apps?