I am looking for some advice from the computer knowledgeable people out there please. I connect to the internet via a dongle, (only way to connect where I am!). I connected up last night and could not connect to any website except ebay and the forum. Just about very other site - gmail, Amazon, one of my Bank websites, came back with the 'Time Out' message. The status panel for the dongle says 'No Internet'. I noticed that as soon as I had connected, there was a Windows Critical Update installed. What I can not understand is, how can I connect to one or two sites and not others? Having connected this morning, Yahoo mail will download the emails, but not let me do anything with them e.g move or delete. Gmail is not connecting. Amazon is connecting in a very basic fashion, but I can do nothing with it, yet the Forum site is working perfectly. I have tried a System Restore, but this will not work due to my anti virus programme, (Avast), which I suppose I could remove and then reinstall.   

Addit: Just realised - as I have no gmail, I will not receive notifications of any replies, so I will have to keep checking the 'recent posts' for any replies!

Can you just try stopping your anti virus program, rather than removing it?

Thank you @Only Me and @Malc . It would have helped if I had told you what I had already done  . I run Malwarebytes Premium and that found nothing amiss and neither did Avast.  However, I have just gone into the 'Default Apps' settings. There was nothing shown for Email, so I selected Google Chrome. In the Web Browser, Google Chrome was shown, but I de-selected it and then re-selected it. SUCCESS!. Everything is working as it should now.  All I can think of, is that the 'Critical Update' last night somehow or other altered the default app for email, which upset something ................... I don't know  . I like Windows, but when something like this happens, it is annoying and frustrating, (if indeed it was the fault of the update!).

I turn off Windows auto updates......... can anything be that critical that it screws your pc....... hmmm I doubt it.
Firewall updates however should not be ignored.