Same problem. Uninstalling and reinstalling the add on forces it to work temporarily, but the problem returns (not sure if its just closing FF or restart that reactivates the issue).
Temporary solution is to revert to version 188.8.131.52 and disable automatic update. Was able to close FF, reopen, and edit entries.
FF dev 60.0b14 (and a few versions back, maybe since b12)
- Decentraleyes, HTTPS Everywhere, UBlock Origin disabled and problem persists.
- LP v184.108.40.206 works fine with the above enabled/disabled.
LP 220.127.116.11 and latest binary installed
Win 10 x64 1709 (build 16299.371, non-insiders)
NOT a problem in Chrome (beta channel), which is on LP 4.9.1.