Try opening a virtual box and running this particular Genymotion virtual machine. If Virtualbox does not complain about downloading VT-X and Android without problems, you can erase VT-X from the list of possible causes of your problem.
To identify the problem, use the quotation marks of the log of recent download attempts (Clear Cache in Genymotion settings).
On my x200 (Win 8), I had problems with the old graphics driver: Intel Series 4 Express (GM45). Since Intel does not offer official drivers, I had to
a) modify the inf file to enable installation on Windows 8
b) allow the installation of unsigned drivers
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