try this
uninstall the client. del the folder from programs. del all cookies and temp files.
reboot the pc. d/load the client. re-install. try
you can try and clear your dns cache
start, run. type...cmd...enter.
type on the black screen, ipconfig /flushdns
[a space between the g and the /]
do that several times.
for the moment use open dns or their servers for the dns
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the above applies more after an internet failure were some sites or countries are unreachable or some change to the voobly server.