Internet security software that conflicts with Gmail
Unless properly configured, third party software (Internet security, pop-blocking, or anti-virus programs) can interfere with Gmail's features and functions. In these third party software settings, you may have to ensure pop-up blocking is not enabled for http://mail.google.com and that cookies (small files on your computer that save Internet settings) are allowed for http://mail.google.com. We recommend visiting the software’s help centers for instructions on how to adjust these settings.
If you have third party security software installed and are still experiencing problems using Gmail after adjusting your software settings, we suggest disabling the software for testing purposes, clearing your browser's cache, and attempting to use Gmail again.
If disabling the software resolves the issue, but you'd still like to use it in conjunction with Gmail, we suggest contacting the software support team for that product. They should be able to recommend settings that allow Gmail to work properly.