Mouse left click not working in model space for 2015 X64SP2

My machine is running Windows 7 Professional and I have the 30day professional version loaded. The mouse left click works normally on the pull down menu's but does not work in workspace.

As an example when drawing a line left click does not nominate the starting point. left clicking produces no result at all - the command line remains static  - prompting for a start point.

If I type in say 0,0 then the line trace appears starting from this point.

What do I need to change in the set up to fix this or is it a fault.

Thanks

John.

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