Go to your firefox user folder
add these lines to user.js
user_pref(“capability.policy.policynames”, “allowclipboard”);
user_pref(“capability.policy.allowclipboard.sites”, “http://docs.google.com http://wave.google.com”);
user_pref(“capability.policy.allowclipboard.Clipboard.cutcopy”, “allAccess”);
user_pref(“capability.policy.allowclipboard.Clipboard.paste”, “allAccess”);
If you don’t have a user.js file just add a text document and rename to user.js.
This seems to work for both google docs and google wave.