Can anybody please tell me what it  is that I have not right here?

On a USB HDD I have a new install Ubuntu 12.04 amd64, a new install of 12.6 drivers (amd-driver-12-6-x86_64.run) installed with the “run” installer. Installed CGMiner-2.7.5 from the “built” version. Extracted in the directory same way as I have been doing for months.
CGMiner runs as usual on BTC (a truly great piece of work) 

However if I try to use “scrypt” for LTC I get these errors. Can somebody please tell me what that means --- in simple terms. 

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[2012-09-09 16:34:18] Started cgminer 2.7.5
          undefined
        const uint xSIZE = CONCURRENT_THREADS;
                           ^

2 errors detected in the compilation of "/tmp/OCLFqZLWF.cl".

Internal error: clc compiler invocation failed.

 
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What is it I have screwed up?
Thanks