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I'm getting, "You must complete a security check before you are able to login to this site. Please do so, and then submit the form." alert, what is this?
This indicates that there is a CAPTCHA (http://www.google.com/recaptcha/intro/index.html) form on the page that must be filled out before the login can be submitted. If there is no apparent CAPTCHA field, please check the 'Edit Form Fields' of the stored LastPass entry and see if a CAPTCHA field was saved on its original creation.
If so, you can delete this field by clicking on the blue [-] next to the field. Save the entry and try again. If you still see issues, please open a support ticket from the link at the bottom of this page.