Unhappy [Q] X10 Simlock issue

hi guys, i have a very big problem with my phone. It is unlocked, simmock status is [ ] for all items. I've already used it for calling surfing, ... welly. But, one day, a dialog prompted asking me a unlock code. By the time, no means to register to any network. I tried. reflashing with seus, changing custom rom like froyobread, cm6 ( my bootloader still locked)
What should I do ?
Is there any methods to resolve that ?
Note: s1tool shows that simlock certificate is not recognized. it is a second hand phone, when i bought it, it is not simlocked, now it. is. i had never touched to the bootloader.
sorry, i am not a native english speaker. greatings from Madagascar