If you have limited connectivity to some sites then there is nothing wrong with the connection between you and cablecom. It could either be a DNS issue (try doing an nslookup on the sites you are trying to reach) or more likely some sort of transient routing issue in the network. However, both of these are very unlikely, and would theoretically affect all cablecom users not just you. I've also never seen it on my own connection, and I use it an awful lot. It's also possible that google may have a mirror inside cablecom's network..

What did cablecom say about the problem when you reported it to them?