Is anyone else having trouble assigning custom ringtones to contacts on the 640xl?

[stephanejap]

I have been unable to customize contact ringtones on my 640xl (build 10512). This started with 10166 and I thought it would get fixed with 10512 but it didn't! I get a popup asking to look for an app in the store and when I tap yes the store opens to a Page not found error! Anyone with a solution to this? (Screenshot below)