Hi, CCleaner is a fairly tame registry cleaner I just went through it on this machine and while I did not active it, I did go through want it found. I could not see how this might have caused your problem, unless you had an errant "add on".
Either way my advice is to not use this feature of CCleaner, the registry does a good job of ignoring those entries and you will never know the difference. Unless your system is unique you would not worry about IPV6, IPV4 is the protocol you need to check. Very often all that is needed is for the router to be switched off, the computer also ,switch the router back on and allow the led lights to indicate it is fully connected then start the computer.
If this fails then a system restore might work (JC's post) or you may need to rebuild the TPC/IP stack.
Go to start, all programs, accessories and right click on command prompt select "run as administrator" at the prompt type:-
press enter then type exit, press enter restart computer and try the connection.