There is a new checkbox on the login page. Normally, when you log into MR, your cookie will be "bound" to your IP Address. In lay terms, this mean that your login session is not good from any other ip address. This is a good feature for security, however in some cases (mobiles, wireless networks), it may be undesirable. In these cases your IP address changes while browsing the site causing you to get logged out randomly or possibly not able to login at all.
Checking the "Bind" checkbox on the login page temporarily negates the default setting. For almost all accounts the default setting is that your cookie is bound to your IP. You will know if this is not the case.
In short: If you are getting logged out randomly or you cannot login (and you get no error message) try using the "bind" checkbox. Especially if you are on a computer you haven't used before. However, most people WILL NOT need this. So don't check it if you don't need it.
