If you are already logged into The Raiser's Edge once, you should get the following message if you try to log in again on another machine:
Error: User (User Name) is already logged in on Machine (Machine Name)
Currently, it is possible to open up the Raiser's Edge under the same username on multiple instances of the Raiser's Edge.
We resolved this issue in version 7.91.5056, patch 4. Download and install the latest patch, which contains all fixes from previous patches. If you are running an older version, download and install the latest version and then the patch.