I have seen plenty of people use the miner software the way you ar ebut you are having some issues. Just as a way to eliminate the possibility its a system issue, consider trying a little different approach.
  Unzip BFG Miner 3.10.0 to the C:\  drive. Not the Windows folder.
  Place a shortcut to Command Prompt on your desktop.
  Open the Command Prompt and Change the directory with          cd\bfgminer-3.10.0-win32 or 64 {press enter}
   C:\bfgminer-3.10.0-win32>_
   now launch with                bfgminer -S antminer:all -o http://stratum.btcguild.com:3333 -u XXXX_1 -p XXX {press enter}
   I have seen that sometimes using "Windows" folder can cause a conflict, usually not, but sometimes.
   Also go over your network cables and devices to make sure that you aren't having interference that is slowing something down, also check windows "system resources" for unexpected extra network activity in the graph.
 An unclocked Antminer U2 default setting should return between 1.44 Gh/s - 1.7 Gh/s as reported by BTC Guild about 660 Valid Shares per hour. With a decent, clean, internet connection and when plugged directly to the computers onboard USB port.