A couple things I discovered when attempting to remove the jailbreak from my iPhone 4s:

1) You cannot just delete the Cydia icon. When you press down on the icon and all the icons start wiggling, you have no option to press the “x” to delete the icon.

2) If you try to reset the phone by going to Settings/General/Erase All Content and Setting, this process will either never start or never finish. You end having to hold Power+Home to restart the phone.

So I tried to restore the phone. I was running 5.0.1 and wanted to keep it that way. Now, the simplest way to do it would have been to put the phone in DFU mode and download and restore the latest version of IOS from Apple. However, as I stated I wanted to try to keep the same version of IOS, 5.0.1 in my case. I downloaded the latest version of redsn0w , unzipped it and ran it. With the phone in DFU mode, I chose Extras/Even More/Identify. This verified that my phone was in DFU mode. Next, I went into Extras/Even More/Restore, and clicked ISPW and browsed to the version of IOS I wanted to restore. At this point, you are prompted to browse to the most current version of IOS (5.1.1 in my case). This is required to upgrade the baseband. If you do NOT want upgrade the baseband, DO NOT DO THIS! Once the latest version of IOS has been identified, you need to tell redsn0w where to find your shsh blobs. I chose remote to pull them from the Cydia servers, Once that is done, click Next and the baseband is upgraded and IOS 5.0.1 is restored. If you want to preserve your baseband, then you need to go the Extras/Custom IPSW route.