Samsung galaxy s (vibrant) network locked again

Hi
I have a samsung vibrant from t-mobile usa and i got it unlocked from t-mobile to use in europe. Firmware is 2.1.update1 and kernel version is 2.6.29. A few days ago i turned it on and it showed "SIM network unlock PIN" with a textbox to write the pin and a unlock and dismiss button. I tried the pin code i got from t-mobile for the first time but it didnt work this time. It just wrote "Network unlock request unsuccessful".
Is there anyway to fix this?? I read somewhere that the radio might have gotten mixed up but i dont know what to do and I havent found any more info. PLEASE HELP!!    

Hi,

My cousin in Australia is having the exact same issue. She bought the T-Mobile Vibrant phone in the US back in oct., 2010. She didn't unlock the phone through T-Mobile. It was done through someone else (not sure how they did it). Anyway she was using it fine in Australia til March, 2011. When she turned on the phone a message "Network Sim Lock" showed up. She told me she got stuck in the middle of a "z4root" installed so she power the device down. The next time she powered it up, the message showed up. Since she never obtained the original unlock code from T-Mobile, we contacted T-Mobile and was able to obtain the code. She tried the code and it still didn't work. Please let me know what she can do to use her phone again. Many thanks...

Ty

I had mine unlock with the code but after I relocked, it would not unlock again. I ended up rooting with SuperOneClick and getting SGS unlock from market. The links are in IronSingh's sig.