why can't i use google on my computer

The browsers that I use is either Internet Explorer 7 or Firefox 3 and if I am trying to type something in the search box of google then i get a weird error message like this:

We're sorry...
... but your query looks similar to automated requests from a computer virus or spyware application. To protect our users, we can't process your request right now.

We'll restore your access as quickly as possible, so try again soon. In the meantime, if you suspect that your computer or network has been infected, you might want to run a virus checker or spyware remover to make sure that your systems are free of viruses and other spurious software.

We apologize for the inconvenience, and hope we'll see you again on Google.

I have scanned my pc with antivirus software but my pc seems to be virus free. So can anyone tell me why can't i use google on my computer? Please help me, thank you

What you can do is download Hijackthis, install and scan in safe mode.. post teh .txt file as an attachment
one of the guys will check through it for you to see if it needs cleaning..

download process explorer (like task manager exept more detail) and check what processes are running and google those processes you dont know..

boot up with the minimum amounts of programs and tasks and see if it solves anything.. if it does, tehn enable/use programs one by one untill you find hte culprit

ping google and see what response you get from it

I think that it might be a virus or adware problem that your are facing. What antivirus are you using. Feel free to refer to some guides and tutorials made on how to remove malwares and adwares from your computer, read here: http://forums.techarena.in/guides-tutorials/456107.htm
http://forums.techarena.in/guides-tutorials/501102.htm
http://forums.techarena.in/guides-tutorials/1196920.htm

I think that this type of problem is usually temporary, if you continue to experience this error, we recommend that you try the following suggestions:

1. Contact your ISP and let them know you are experiencing connectivity problems with Google/Yahoo. Your ISP will
be able to address and resolve this abnormal activity.

2. Temporary solution is type the code to continue the search.

3. Check that you are not using any third party software program or
application such as pagerank to access Google/Yahoo.

4. Make sure no spyware and viruses on your computer.

Source: chicagotech.net