...you need to fullflash your phone using testpoint and disable "write bootcore protection" (with X65flasher). Click on Start-> Run -> type: cmd -> go to your X65flasher folder (cd D:\............) and type: x65flasher /b. X65Flasher window will appair, make testpoint and click to Connect. Disconnect testpoint (in three secconds) and after initialisation (appair Siemens SL75 0089,880D) click on Write Flash. Wait to finalise writing flash ( aprox. 1 hour), close X65Flasher and open Papuautils. Go to the Codes menu and write in SKEY case your SKEY (or any number, example 12345678). Go to the Flash menu, check ????? OTP, Recalculate Keys (check in Flash - automatically is checked three options, don't touch), Pause. Make testpoint and click on Do the Job! . Disconnect testpoint (three secconds) and wait to calculate the new HASH and BootKey. Veryfy again (enter in Service Mode) if your phone is unlocked (Status: Factory Mode). Fullflash file posted by me (link to rapidshare) is tested and worked (Firmware 47, Language pack 4).
For me this is working manny, manny times on S-Gold phones with bootcore destroyed.
dagos