I had a logon problem not after a cpu change, but a cpu FAN change, believe it or not! My computer shut down after the fan quit because of thermal protection. Even though I could change a fan, I went to my tech to have it done because I wanted the computer fully checked to be sure nothing happened during the meltdown. I came home, could do anything on my computer but eq.
Figured eq got corrupted somehow, re-installed it, which is ever so much fun as I have the original disk, and each individual expansion. Nope, wasn't it. Bought the new platinum, installed that. Nope, wasn't it. Called Sony, two hours of online chat/phone chat with tech and they kept pointing the finger at my isp. Called the isp, they walked me through resetting all sorts of stuff in the modem, even though gameplay was fine up until the fan quit. I was IN eq when the fan quit, which is why I suspected corruption of files.
Finally, my isp sent me a new modem, said that will fix it. I had my doubts as this connect problem hadn't existed before the fan quit, and now I couldn't connect either from my house or from my tech's store, which uses a different isp. That didn't help.
So I went out and bought a different game, played that for a month, was ready to uninstall eq when I clicked on the icon one last time to masochistically see the error box pop up and tell me it couldn't make a connection. This time I logged in and have been able to play ever since.
Go figure.
Z