Predictive Name Delay

[longers1]

I have an Iphone 4. Since upgrading to the new software last year, whenever i put in someone's name, it takes at least 15 seconds to recognise it and come up with the list of options. This happens on email and on text messages. I took it into the apple store and they hadn't seen this problem before and weren't much use. I have tried completely restoring but as soon as i put my contacts back on, it happens again. Anybody know how to fix it? Any help appreciated. Thanks