I am having issues with my CakePHP application. This seems to be happenining only in IE, and only on certain computers. It is consistent on the computers where it is happeni
My suggestion is that you take a look at the packets directly, to see what is happening to the cookies.
Install Wireshark on your client machine, and connect to a remote web server. (Wireshark will ignore localhost traffic.)
My suspicion is that your cookies are either getting mangled (I once had some cookies mangled by PHP!) or they are stuck (which would be IE's fault). Either way, you will have more information about what's going wrong.
As a last resort, check the user-agent string in the code for the offending / unsupported version of IE, and urge people to upgrade.