I have a fully unlocked iPhone and use it with a three contract sim card…
From time to time, especially at home, ive been experiencing problems where pressing the home button takes ages for my phone to actually wake up, and then often when it does wake up, the slide to unlock screen is frozen, and I have to wait longer before I can actually slide and unlock.
Ive tried loads of things to try to figure this out, I am jailbroken, so wondered if it was that that caused the problems, but after putting the phone into flight mode, the problem went away..
After some digging around, I tried manually selecting my carrier – specifically the 3 3g one. Whilst this is far from ideal as it locks me to three’s 3g network, which means that should I go outside of that I will not automatically fall back onto the 2g infrastructure, it does seem to have sorted my problem.
More digging and reading suggests that when the phone switches from 3g to 2g, it can some times be a slow and painful process, and especially so with three’s network, as it seems they utilise other peoples 2g infrastructure, which would explain why I dont see this problem with a vodafone iPhone.
So if you are on three, it might be worth trying this, but remember you are likely to get more No Service messages if you go outside of a covered area and will need to manually either select automatic to get it back, or manually chose an alternative compatible carrier.