sharke
I'm still not sure I understand the need to keep a machine disconnected from the internet. I understand the issue with wi-fi and spikes, but a cable hookup doesn't cause any problems and you're not going to infect your machine just by having it plugged in. The only virus I've ever had was because I opened an .exe from an untrusted source, and boy did I learn my lesson. Unless you're being wantonly careless then there is absolutely no trouble at all.
I hear people say "the DAW is my living therefore I'm not taking any risks with it," but I also know people who work in other fields like 3D animation, video production, photography and design whose livelihoods also depend upon a fully working machine crammed with powerful software, yet they're very much connected to (and using) the internet on those machines every day. Music producers are the only people I ever hear express fear of connecting their machines. It's weird.
This is the thing...
1) If you don't ever update any software of any sort fine, go ahead stay off the internet. It will probably work forever.
2) What generally happens is people do update their software (Sonar/plugins etc) then one day they wonder why it doesn't work (mainly because their dependencies are too old e.g. firmware, drivers, libraries, windows update etc).
3) Updates contain more bugfixes than new bugs. Also more often than not performance is improved (yup in the past it often would be the opposite!). On the RARE occasion there is a problem you can rollback and one would hope you have backups (although with Sonar itself not so rare, sorry to say that).
If you are updating any of your software you are best staying completely up to to date, otherwise you may end of experiencing strange and mysterious bugs that nobody else is getting..
Otherwise freeze your PC, take it off the internet. Don't mess with it at all. Don't install or update anything.