Do this things

1. Take out the simcard and rebootthe iPhone
2. Try and call the phone using either your home phone/office phone or another mobile and see what is going on

If this is still problematic, then try resetting all network settings.

Hopefully this will solve all your problems.

This is really problematic. The jailbreak is not worth not being able to receive calls. If all else fails, you need to wipe your iPhone and restore to the latest firmware and see if you still have the problems. If after restoring you still have the issues, then it is time to send in for warranty service.

Google on how to check your 3Gs bootrom version. If you have the old bootrom version then the 5.1 jailbreak will be untethered. If it's a new bootrom version, then it will be tethered just like everyone else.

That is news to me. 4s or any A5 devices cannot be jailbroken publicly as yet as far as I know.

Absinthe is for 5.0.1. Not for 5.1

The site is BS.

Yes, the latest Gevey can unlock 4.11.08

Check with bro WimpyKid about stocks and prices.

Latest redsn0w should do the trick.

Without saved SHSH, no shop can downgrade. If they say they can then they are conning you out of your money.

If it's a local set, it should be factory unlocked. Try resetting the network setting and try again. If that doesn't work, take out the sim and re-insert and see.

if all else fails, backup your iPhone and do a fresh restore.

Cydia usually saves them during the signing window but sometimes it doesn't as well so to be safe, don't depend on cydia 100%. Just use TU and you should be okay.

That could be the reason. Why did you skip the activation again? It's factory unlocked so you shouldn't worry about sim activation.

You should be able to jailbreak your iPhone 4. It will be a tethered or untethered jailbreak depending on the current firmware version you have.

You should not have any issues with updating apps that you purchased from the apps store.

Read first post. And this only applies to a tethered jailbreak for the iPhone 4 and 3Gs. iPhone 4s cannot be jailbroken on 5.1

1st post has all the info. I usually will update the first post if there is any new development.

Once a bug is found, a new version is released to resolve the bug. There are cases where you need to use a specific version of redsn0w (usually if you are using the iPhone 3G) but in most cases, just use the latest version of redsn0w.

I believe you need to be an existing AT&T customer to be able to unlock. If you buy a locked set but was never an AT&T customer, then I don't think AT&T will unlock the iPhone for you.

Shouldn't be a problem. The iTunes will be able to backup/sync your 5.0.1 jailbroken iPhone 4

Ahh, if you are still on 4.x.x you cannot upgrade to 5.0.1 without saved SHSH since apple no longer signs 5.0.1

Check Cydia and see if it has saved the 5.0.1 for you. If it has, then you maybe able to upgrade to 5.0.1 via iFaith. If cydia did not save the SHSH for you, then you are out of luck. You can only upgrade to 5.1

Respringing (there should be an option if you have SBSettings) will solve the issue.

If your iPhone 4 is jailbroken, check Cydia and see if it has the 5.0.1 SHSH saved for you. If it does not have it, then you're out of luck. If it does, then you may be able to upgrade to 5.0.1 via Custom Firmware with iFaith.