iCloud not backing up iPhone 4s data?

I have an iPhone 4S, for most of the time I back up on iTunes via my PC, but today I wanted to turn iCloud back up back on, just in case ya know,...well I turned it back on and hit the back up now tab,...the phone told me it was "estimating time of back up" and made no progress, it did this for 10 minutes and then said back up could not be completed and just gave me the date of the last back up I did before. I called apple cares and they told me to reset the network settings, restart the phone and restart the router. I did all this and nothing has worked. I dont think its a problem with the router because I can turn wifi on on the phone and surf the web just fine. Its just iCloud will not back up my phone....any suggestions or any ideas as to what is going on?? Thanks guys and gals.