iCloud constantly displaying "23 hours remaining" on iOS5 with iPhone 3GS

On iPhone 3GS, under Settings > iCloud > Storage & Backup, it constantly displays "23 hours remaining" when supposedly backing up, and the status bar does not move, but rather hangs about an eigth of the way across.

It states: "Last back up: never".

It eventually gives up and says that it can't back up.

I am connected via WiFi, plugged in and charging, and have selected "Back Up Now".

It claims that it will back up everything when plugged in, locked, and connected to WiFi. However, after leaving it in that exact state overnight, still absolutely nothing happened.

I also have an iPad 2 on iOS5, and the iCloud backup worked absolutely fine.

Is anyone else experiencing this?

Many thanks in advance.