Hi Par,
Most likely problem is file system permssions are not correct on the new server. You need to make sure the /Data folder and the /App_Data folder are both writable by the web process user. You may also need to delete all files from the /Data/systemfiles folder as they may have funky permissiosn on them from the previous server, if the folder is writable they will be re-created.
Make sure you are using the new Web.config file as it has the correct settings for the locations of the editor scripts. Make sure that you uploaded the /ClientScript folder without any transfer errors as missing files could cause the tabs not working and the editors not working.
If you continue to have problems look in the mojoportal log under Administration > System Log or by downloading the file /Data/currentlog.config.
Of course if file permissions are not correct it may not be able to write to the log.
Hope it helps,
Joe