Nov 16 2011
Apple’s iOS 5.0.1 seems to have created a glitch with the Contacts app for certain users, according to various sources and several posts on the Apple Support Forums. Many of the iPhone users have had problems after updating to 5.0.1. The iPhone was no longer able to associate address book contacts with other apps. Opening the Contacts app would display all the right names. But using the iMessage texting app or even making a phone call would fail to remember the name of a contact and just display the person’s phone number.
Apparently, this issue has been experienced by a certain iPhone users,like users who have a Verizon iPhone 4S and who updated to iOS 5.0.1 using the OTA (over-the-air) method rather than installing it through iTunes on your computer.
As stated on Redmondpie.com, You can resolve this issue by following the steps shown below: