GUI Miner no responses to getwork, and Verification failed I just starting with mining today I have everything set up for slush pool on 
GUIMiner - v2012-12-03 .  I'm not sure what is wrong but this is what the console says

2013-06-21 01:37:26: Listener for "GPU Miner" started
2013-06-21 01:37:28: Listener for "GPU Miner": stratum.bitcoin.cz:3333 21/06/2013 01:37:28, checking for stratum...
2013-06-21 01:37:28: Listener for "GPU Miner": stratum.bitcoin.cz:3333 21/06/2013 01:37:28, started OpenCL miner on platform 0, device 0 (Juniper)
2013-06-21 01:37:28: Listener for "GPU Miner": stratum.bitcoin.cz:3333 21/06/2013 01:37:28, no response to getwork, using as stratum
2013-06-21 01:37:39: Listener for "GPU Miner": stratum.bitcoin.cz:3333 21/06/2013 01:37:39, Verification failed, check hardware! (0:0:Juniper, a4627d39)
2013-06-21 01:37:51: Listener for "GPU Miner": stratum.bitcoin.cz:3333 21/06/2013 01:37:51, Verification failed, check hardware! (0:0:Juniper, 9fcd8ac2)
2013-06-21 01:37:52: Listener for "GPU Miner": stratum.bitcoin.cz:3333 21/06/2013 01:37:52, Verification failed, check hardware! (0:0:Juniper, 87fcf304)
2013-06-21 01:37:55: Listener for "GPU Miner": stratum.bitcoin.cz:3333 21/06/2013 01:37:55, Verification failed, check hardware! (0:0:Juniper, 5aa4b0f1)!


I also took a screenshot of the settings I have chosen here.
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.