P990I Debrand & World Generic 1 "Invalid sim"

Hey ,
I would like to ask you guys a question but i will explain my situation first,
Well .... i got a Sony Ericcsson P990I from someone and it was Vodafone UK but it would take my O2 UK sim fine but as you probably guessed i iwas getting sick with all the startup screens and branding of vodafone and decided to debrand it to world generic 1
all went to plan and it was now starting up with sony erricsson and not vodafone and then a phone lock popped up witch was 0000 but then after that it said Invalid sim :S so then i tried a vodafone sim witch the phone was branded with but that still wouldnt work from then on ive been trying to find out a way to fix this problem and had no luck and as you guessed my question is

1) How do i get rid of the Invalid Sim on world generic 1 - SE P990I

Thanks in advance