If (when you can connect to the internet) you can only visit regular sites; and not any form of Update Service or Security sites, then it sounds to me that you are still infected in some way.
Read through the link (provided by Grif-M); the programs listed will provide you with the necessary tools to get your computer in order (if infected), also it will provide you with the information needed if there are programs that are conflicting with each other (eg: more than one antivirus installed).
About 3 days ago my inspiron 1520 started acting funny. I have a Linksys wrt120n wireless router and 2 other laptops that connect and work just fine. First i noticed this computer would always boot up in windows classic theme. I would always have to restart themes to get the xp theme to show up. Also, windows firewall would always be turned off when you booted the computer up or did a restart on it. The other problem it has is no connectivity. It always states that it is acquiring network address and has an ip address of 0.0.0.0.
I have malwarebytes, avg free, and spybot and have ran scans on all these programs with no success. This sounds like a virus to me, but i am no expert in computing.
Also, today by the grace of God somehow it connected to the internet and I did an update to all virus programs and attempted to connect to microsoft and windows update. It would go to all normal websites, but would not go to the microsoft windows update site.....Thanks for any help you can give me.