This usually indicates speculative attacks (usually from someone whose system is infected) not that your OS isn’t up to date, the attempt to exploit doesn’t know the OS, much less if it is up to date. But it does indicate that the avast Network Shield seems to be catching it when this happens it is because your firewall isn’t intercepting these exploit attempts.

What is your firewall ?
What Operating System are you using ? is it up to date ?

This is the price of protection, life is about compromise, and a good firewall is an absolute must, but it shouldn’t get in the way so as to noticeably slow your connection, answering the what firewall do you use will help. I personally wouldn’t take them up on the offer of the upgraded security package either as I feel their support is severely lacking already and there are many good firewalls out there at a reasonable price or even free.

I would say switching ISP isn’t an option, but take responsibility for your own protection, no ISP can provide workstation protection from a server based security option. You have to have the security programs installed on your system and I also wouldn’t take any ISP security package as IMHO they don’t select the best package for you, rather the best package for them.

As I said the silent mode option isn’t recommended, that is only masking the possible symptoms, not treating the disease and we haven’t even established which provider is alerting you. If they are all dcom style attacks then I suspect they are Network Shield alerts.

If you can provide us with a sample of the alerts (common groups), check out the avast! log viewer (right click the avast icon and select it) and look in the warning section. We want the virus name, file name and location, either HDD path or Web URL, etc.