Can a computer connected to a DSL modem connect to a cable modem without change?

When a computer is normally used with a DSL modem can it be connected to a cable modem?
Will Outlook Express account have to be changed?
I ask these questions because I cannot update avast on the cable modem, I get error "cannot connect to server"
Same problem with Spybot S&D will not update when installing.
Outlook express account will not send mail. Outgoing server is set to "mail.i2k.com". Should another account be setup for the cable modem connection?
Two full days of frustration.
Ran Malewarebytes, Superantispyware.
A virus backdoor.tdss.565 was removed but there may be remnants hiding.

Hello, and welcome to GeekPolice.

Please note the following information about the malware forum:

• Only Tech Officers, Global Moderators, Administrators, and Malware Advisors are allowed to give advice on removing malware from your computer.
  
• From this point on, please do not make any more changes to your computer; such as install/uninstall programs, use special fix tools, delete files, edit the registry, etc. - unless advised by the staff I noted above.
  
• Please do not ask for help elsewhere (in this site or other sites). Doing so can result in system changes, which may not show up in the logs you post.
  
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  Reply to this topic with the word BUMP, or
  see this topic.
  
  
• Lastly, keep in mind that we are volunteers, so you do not have to pay for malware removal. Persist in this topic until its close, and your computer is declared clean.

---

Note: the following tool is to only be used under the guidance of a malware helper. In the event you already have the tool, please delete the old copy and download a new copy.

Please download ComboFix from BleepingComputer.com

Alternate link: Forospyware.com (Click the green button on the page to download it).

Rename ComboFix.exe to combo-fix.exe before you save it to your Desktop

• Disable your AntiVirus and AntiSpyware applications, usually via a right click on the System Tray icon. They may otherwise interfere with our tools A guide to do this can be found here
  
• Click Start>Run then copy paste the following command into the Run box & click OK "%userprofile%\desktop\combo-fix.exe" /killall
  
• As part of it's process, ComboFix will check to see if the Microsoft Windows Recovery Console is installed.
  
  *NOTE*: If you already have the Recovery Console installed, ComboFix will skip this part and will continue scanning for malware.
  
  With malware infections being as they are today, it's strongly recommended to have this pre-installed on your machine before doing any malware removal. It will allow you to boot up into a special recovery/repair mode that will allow us to more easily help you should your computer have a problem after an attempted removal of malware.
  
• Follow the prompts to allow ComboFix to download and install the Microsoft Windows Recovery Console, and when prompted, agree to the End-User License Agreement to install the Microsoft Windows Recovery Console

Once the Microsoft Windows Recovery Console is installed using ComboFix, you should see the following message:

• Click on Yes, to continue scanning for malware.
  
• When finished, it shall produce a log for you. Please include the contents of C:\ComboFix.txt in your next reply.
  

Jay,
The problem is solved.
Because I couldn't get Avast updates, I visited http://forum.avast.com and found the following advise:
"If you open the Avast GUI > Settings > Updates > Details > Update Parameters...do you have anything checked off under these settings ("I only connect to the Internet using a dial up modem" or "My computer is permanently connected to the Internet")? What is checked if anything?
I checked the later, always connected.
Also:
If you open the Avast GUI > Settings > Updates > Proxy Settings > do you have anything checked off here ("Direct connection/ no proxy" or is "Auto Detect/Use IE Settings")? What is checked if anything?
I checked "Direct connection/no proxy"
With those two items checked the problem was solved. Apparently I had successfully removed all viruses and this cured a Proxy problem.
All is well...

I requested ComboFix to be run, if you are getting the detection of TDSS.

The TDSS rootkit cannot be removed by a user alone, nor can be removed by an antivirus. It takes specialized, powerful removal tools to get it disinfected.