First of all check if /NEPTUNE and subnodes are activated in transaction SICF.
Solution 1: Update SAP GUI.
- Update to SAP GUI 7.30 Patch 10
Solution 2: Update your host file.
- In Windows Explorer go to \Windows\System32\drivers\etc and open file 'hosts'
- This file contains the mappings of IP addresses to host names
- Add entry of your SAP system: <ip address> <hostname>
- Save 'hosts' file
Solution 3: Change Theme
- In the SAP menu go to Neptune - Design - Settings and set Theme and Font Size
Solution 4: Enable old Neptune editor
- In the SAP menu go to Neptune - Design - Settings and enable Old Editor
- Click Save button