Gmail – Using ‘Send and Archive’ with Keyboard Shortcuts

As it works for me with the same list of labs and Chromium 13.0.782.215 and you said you're using the same version, I suspect it'd either be something else in your GMail settings (which you ruled out when the Incognito Window didn't exhibit the problem) or something in your Chrome profile.

I can see three potential sources for the problem on the client side:

1. Flawed extension. (Fixed by a new profile. Fixed by an Incognito Window unless you've chosen to allow the broken extension in Incognito.)
2. Corrupted profile. (Fixed by a new profile. Anybody's guess whether a given instance of corruption will be fixed by Incognito Window.)
3. Strange config tweak in your Chrome. (Fixed by a new profile. Not fixed by Incognito Window.)

Chrome has primitive support for running with multiple profiles which you can use for testing. There's a quick-and-dirty approach and a cleaner approach for long-term use.

Since you said the Incognito Window fixed it and you didn't mention any other problems in your Chrome, my guess is that it's probably a bug in one of your extensions that's causing the extension to grab the Tab keypress but then make the flawed assumption that injecting a tab character is the way to say "on second thought, use the browser's native handler after all".

Use the down arrow to select the auto complete you want then press TAB.

This will populate the search box with the selected auto complete item, add a space and position the cursor after the space without executing the search. You can then continue to add search terms, using the down arrow and TAB where more auto complete suggestions are applicable.

Only when you've finished with your search terms, hit ENTER.