Just a thought.. How are you opening the 2 scripts to copy between as there are 2 different ways to open scripts and 1 allows copy/paste the other doesn't.
I.e. From the Agent Procedure Menu you can select one script and click Edit Procedure , then from the menu tree again click on anther script and edit. This will open a new browser tab for each procedure.
This does NOT allow cut/paste
But if you open the first script to edit and then from within the actual script editor select the OPEN option from the script menu and open your second srcipt you can cut/paste
In the image attahed the top shows 2 scripts in 2 browser tabs.
The lower part of the image shows the Open option from within the Script editor
I'm using Chrome 26 and it works fime for me