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Accepted Solutionby Claudius
The click to call interference only occured after I installed the latest version of Skype. Since I deleted click to call no more problems.
Also after installing the latest version my wireless keyboard and mouse stopped working intermittently. Again no problems since de-installing. Why would Skype affect wireless - no idea but equllay no idea why Skype should interfere with Excel functionality.
Can't explain the wireless interference though. Probably just coincidence.