Automation overwrite

Hi there!
I’Ve used Cubase SX3 a Long time and now I’m trying the Cubase 7 Trial. One question came up with Automation modes: I always used “overwrite” mode and only the write button (not the read) when writing Automation. So I clicked on the (left) starting point, set all faders and then started playback while rewriting Automation data. Now I tried the same in Cubase 7 and it didn’t work:
.) The Write button can only be activated together with the read button. So I can’t change the fader position in “stop mode”.
.) When playback starts the faders follow the old automation data.

Do you know what I did wrong - or what has changed in automation from SX3 to 7? I can’t find any usable Information, neither in the docs, nor the Forum… :confused:

Thank you!