I had the same problem.
Now I’m new to WP and I’m no php expert so keep that in mind.
Since the problem only happens on the front page I added an elseif to the php code between my title tags in my header.php.
My code looks like this:
<title><?php if (is_home()) { echo bloginfo('name'); } elseif (is_front_page()) { echo 'my_homepage_title'; } ... ?></title>
It may not be the best solution, but it works.
According to the link iridiax posted, the bug should be fixed in 2.7.2.
