Since 4.0, spaces translate to question marks (for me at least), meaning that if I type "gi this and that" (gi being google image) into the command line prompt, Google image will appear in the default browser and having searched for "this?and?that?". Same goes for any search engine I add.
Running Vista 64.
Edit the search engine and set "Replace spaces with" field with the empty string. Also I recommend to update Command Line up to version 4.1 (just published). There was a problem with updating.
That didn't work Yuri, though I think perhaps the updated ruined my settings. For example, I couldn't add anything to the replace spaces field, I wasn't allowed to enter anything, but I created a new search engine entry that was identical, and then it worked. I'll just delete them all and re-create them. Thanks for pointing me in the right direction!