Not sure why that should happen, but I do hate when I mistype a URL and the browser jumps to a search page denying me the opportunity to edit my own typo. Therefore I disable searching from the address bar in IE:
Tools > Internet Options... > [Advanced] > Scroll down to the section "Search from the address bar" and select the "Do not search from the address bar" option.
This will deal with the symptom but maybe not the underlying cause.
(Just a thought: you're not typing URLs into the Google search bar instead of the IE address bar are you...

I've done that occasionally inadveretantly before

)
K.