I am unable to install the gmail checker from the sample extensions. I can install the build bot and subscribe extensions but not the gmail checker. Any ideas would be appreciated. I'm on 3.0.190.1 by the way.

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Do you get any error message ?
Do you see anything related to GMail checker under chrome://extensions/ ?

Here is the message I get. The same error shows at the top of chrome:/extensions

Errors
Could not install extension from 'C:\Users\justin\Downloads\gmail (5).crx'. Could not open file.

I have tried deleting all of the gmail.crx files in my downloads folder thinking that it didn't like the duplicate file but that didn't help either.

I've had that happen every now and then while testing out new extensions. Make sure you are opening chrome from a shortcut with --enable-extensions before trying to install the extension.

You can also try this:

1. Restart Chrome
2. Navigate to any webpage (eg www.google.com, anything but chrome:// pages)
3. Drag the .crx onto window.

thanks! Dragging it from Windows explorer to chrome worked