What is the Operating system installed on your computer?
Which version of Internet Explorer are you using?
This might be happening due to the security software, try disabling the security software and they try going online and check if you get the same error.
If the error does not persist when you disable security software try uninstalling and reinstalling the software or try updating the same.
If that does not help try putting the computer in clean boot and check which of the background program is causing the issue. To help troubleshoot error messages and other issues, you can start Windows Vista by using a minimal set of drivers and
startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts.
The steps to be performed in clean boot are given below:
1. Log on to the computer by using an account that has administrator rights
2. Click Start, type msconfig.exe in the Start Search box, and then press ENTER to start the System Configuration Utility.
If you are prompted for an administrator password or for confirmation, type your password, or click Continue
3. On the General tab, click Selective Startup, and then click to clear the Load startup items check box. (The Use Original Boot.ini check box is unavailable.)
4. On the Services tab, click to select the Hide all Microsoft services check box, and then click Disable all
Note: Following this step lets Microsoft services continue to run. These services include Networking, Plug and Play, Event Logging, Error Reporting, and other services. If you disable these services, you may permanently
delete all restore points. Do not do this if you want to use the System Restore utility together with existing restore points
For further information on clean boot please follow the below given link:
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7