Using the "Bind to IP Address" option does not work if your IP address changes regularly (such as every time you make a new connection to your ISP). If you have selected this option and cannot remain logged in, unselecting it may help.
i think this is a bit too specific. my IP doesn't change, and my ISP uses a transparent proxy, but its IP doesn't change either, so i've not had a problem with this option. however, i recently had a problem where it seems like the request comes from a different IP for one particular page, so unselecting this option helped. maybe it could be worded more like:
Using the "Bind to IP Address" option does not work with some Internet Service Providers (particularly if your provider uses a proxy for web access, or your IP address changes regularly). If you have having problems remaining logged in with this option selected, unselecting it may help.