Session cookie expiry based on local time

[eluser]CJL01[/eluser]
I'm using database sessions. I think I partially resolved this by urlencoding $cookie_data which forms the content correctly and allows the cookie to work correctly with the db... at least on Firefox. Here is the cookie I now see on Firefox;

Code:

a:4:{s:10:"session_id";s:32:"e11c2ac0e347bc7be184ef02ea41adb8";s:10:"ip_address";s:11:"70.34.79.36";s:10:"user_agent";s:50:"Mozilla/5.0+(Windows;+U;+Windows+NT+5.1;+en-US;+rv";s:13:"last_activity";s:10:"1281964868";}6edae689ed89106fa2e4f5c64e9d6795

While this works perfectly on Firefox, the same site viewed with IE doesn't work - the cookie doesn't appear to be registered at all.