I know that a number of people have experienced problems with this issue. In a previous post, I indicated there was a possible workaround: just create a new character seemed to fix the problem. I think I have finally come across the problem and the real solution, which I confirmed this am. If you log in and get this screen, exit and immediately check your virus protector software for updates. I use BitDefender Total security myself. Was logging in this am, worked through a few toons with no problem. All of a sudden on camping to next character, up pops the "Create a new toon" screen. I immediately exited, checked BitDefender and lo and behold, there was an update. Applied the update and immediately logged back into game and my next character. Since I don't believe in coincidences, I'm concluding this may be the issue many of us have experienced over the last month or so. What triggered it, I can't say, but the evidence suggests it may be your anti-virus software creating this situation.
I use the same virus program and it also has a problem with EQMaps and other 3rd party software used for EQII.
Make sure you open Bitdefender and add these to your "apps." I can always tell when an update has arrived now that I know what's triggering the "Create a new character screen," haha.