Internet Explorer 6.0, URL entry issues

In the past, I was able to get away with entereing a URL in the Address line with just www.------.com, or even sometimes ------.com. The http:// portion was never necessary. Now recently, I received some type of Spyware/hijacking of my start page and have to enter http:// for every address or it does not recognize the address, it will give me an error saying
"Cannot find www.----.com, make sure the path or internet address is correct. I have already deleted the start page problems and I no longer have an issue there. But I can't seem to get the ease of entering URL's back to normal.

I have Windows XP. I also have the following, Sygate Firewall, Avast Virus Protection, Bazooka, S&D, Spyware Blaster, AD-Aware, Hijack This, Winpatrol. I have used them all to look for the culprit, but every log seems to be clean. I have also checked IE 6.0 settings, but can't seem to see anything there.

What have I overlooked?

Thanks for the help.

 

No, I didn't have it on. But I never had it on before and I was still able to enter URL w/out the http entry

 

Auto Complete is only good on URLs you have visited previously. A workaround until you find a solution is to hit Ctrl-Enter instead of just Enter.