hi
100000005
try this
uninstall the client. del the folder from programs. del all cookies and temp files.
reboot the pc.
install this free app: [You must login to view link]
do the cleaner and registry clean ups. d/load the client. re-install. try
or
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.
or
for the moment use open dns or their servers for the dns
208.67.222.222
208.67.220.220
[You must login to view link]

the above applies more after an internet failure were some sites or countries are unreachable or some change to the voobly server.