When installing in Chrome, I see: Extensions, apps, and user scripts can only be added from the Chrome Web Store.
Google is changing their restrictions for installing extensions in Chrome, requiring all users to download extensions from the webstore rather than from a website. Currently users who need to install the extension directly in Chrome must follow these steps as a workaround: http://support.google.com/chrome_webstore/bin/answer.py?hl=en&answer=2664769&p=crx_warning for "Steps on adding extensions from other websites".
The easiest way is to download the package from LastPass.com and drag the downloaded file directly into your Chrome Wrench > Tools > Extensions list. This will install the extension into Chrome. This process will be necessary if you plan to install the binary version of LP, as this version is not currently available in the Chrome web store.
You can also use the full installer: https://lastpass.com/installer to work around the restriction.