By the way, talking about 3.0, here is another problem of screen:

$ screen -S X
[detached]
$ screen -S Y
[detached]
$ screen -r X
$ screen -r Y
[detached]

And here I'm in screen named X, but I cannot detach him. Even after
exit, there will be:
$ screen -list
        5840.X  (Detached)
        5762.Y  (Attached)
And then:
$ screen -r X
$ exit
$ screen -list
        5840.X (Attached)

Screen somewhere confuses with ttys. I did't try this in -current, but
this problem still exists in 3.0_STABLE.

-- 
Best regards,
Mindaugas