I have this happening as well on One computer. to define this a bit more, The account is logged in, and the server selected. Next thing I should see is the character selection screen. the time this screen takes to show/load is several MINUTES.
When I do the above on a different computer, the time is short, i.e. a few seconds or what I remember as a normal amount time for City of Heroes.
I've gone so far as to create a second account to test this. Both accounts, on my windows 7 computer take minutes for the "Retrieving Character list" to happen. On my Windows 10 computer, both accounts load in seconds to that screen.
Troubleshooting wise, I need more data. This is leaning towards operating system difference, but could just be something related to having installed/removed/reinstalled the game on the Windows 7 system several times now.
I.e. I am not sure if there are 'old' parts looking for the game at the 'old' locations and only 'working' once the actual game location is 'found'.
I think, I will try installing (clean) on a different windows 7 system and see what happens there.