Internet Explorer unable to set cookies for one site

[Yasunari Kato]

I'm using a phpunit extension phpunit-selenium to run a test on my website using selenium grid, but whenever I try running tests on Internet Explorer, I get an error message stating:

Unable to add cookie to page (WARNING: The server did not provide any stacktrace information)

 The issue seems to stem from phpunit-selenium trying, but unable to set a cookie "PHPUNIT_SELENIUM_TEST_ID."

I found example code of setting and removing cookies from here, and the interesting thing is the code from the link executes just fine on IE, displaying contents of the cookie, but when I try to add cookies to my site, it fails.

I've tried possible solutions, such as getting the website before attempting to set the cookie, and turning "Protected Mode" off.

Is there another security setting on IE or something that I'm missing?