GUI Miner no responses to getwork, and Verification failed
An answer can be found on bitcoin talk

https://bitcointalk.org/index.php?topic=177855.msg1852355#msg1852355

Quote from deepceleron on bitcoin talk


  This is your GPU returning invalid hashes from it's kernel. This is
  because new drivers are crap for older cards.
  
  
  Uninstall AMD APP SDK
  Uninstall AMD Catalyst Install manager: choose "uninstall all software", make sure you have only a VGA driver after restart.
  Manually remove these files not removed by the installer; any other obvious ATI files with the same file date:
  C:\Windows\System32\amdocl64.dll   C:\Windows\System32\amdoclcl64.dll 
  C:\Windows\System32\OpenCL.dll   C:\Windows\SysWOW64\amdocl.dll
  C:\Windows\SysWOW64\amdoclcl.dll   C:\Windows\SysWOW64\OpenCL.dll
  Install just the Catalyst 11.11 driver package (no SDK is needed; the AMD APP runtime is included with driver)
  Mine just a bit slower on your 6870 than a 5830 would.
  
  
  Better:
  - use cgminer
  - set phatk worksize to 256 and underclock GPU RAM to 300MHz for best power efficiency and higher hashrate


The big thing to take away from this:
set phatk worksize to 256 and underclock GPU RAM to 300MHz for best power efficiency and higher hashrate

A suggestion i can give you is that bitcointalk can be a great place to find the answer to a lot of off the wall questions related to bitcoin or any alt-coin.