The most common reason the PNR Builder screen is Not Responding is because the option to send PNR data as one transmission is enabled. Disabling that option should resolve the trouble you're encountering.
To disable the "Send as one transmission" option:
- Click on Global Defaults > Merge to PNR Defaults > PNR Settings
- Select your GDS from the drop down list at the top of the window
- Make sure the box "Send as one transmission" is Not checked
- Click OK to save your changes
