Windows uses a file named Hosts to make it quicker to get to some Web sites. The Hosts file is not needed for Windows to run correctly. On most computers it will have only one or a few entries. However, if it is changed by a virus, worm, Trojan, or spyware, one or more lines in this file can prevent you from getting to Web sites, including Symantec's. I would suggest you to check and clean the Windows Hosts file.
Find all hosts files in Windows XP:
1. Click Start > Search.
2. Click All files and folders.
3. In the "All or part of the file name" box, type:
hosts
4. Make sure that "Look in" is set to "Local Hard Drives".
5. Click More advanced options.
6. Check Search system folders.
7. Check Search subfolders.
8. Click Search.
9. Click Find Now or Search Now. After all files are found, delete any extra lines(search could take a few minutes).
For each Host file that was found in the search, do the following to delete any extra lines:
1. Right-click the file and then click Properties.
2. In the bottom section of the Properties dialog box, make sure that the Read-only attribute box is not checked. If it is checked, remove the check mark.
3. Click OK.
4. Right-click the file again and then click Open With.
5. Uncheck the Always use this program to open this program check box.
6. Scroll through the list of programs and double-click Notepad.
7. When the file opens, delete all the entries in the Hosts file, except for the following line:
127.0.0.1 localhost
8. Close Notepad and save your changes when prompted.
(Make sure that you check all the Hosts file found during search)
You also want to make sure that Avira program is completely removed from your computer as this issue may happen due to conflicts caused by the remnants of Avira program. You can check the manual uninstallation guidelines for Avira program from their FAQ Page.