HI,
Ever since I updated to Mavericks, just like a lot of other people, My Encore 5.1 would not open. I found a solution and now Encore runs fine on Mavericks.
The solution, posted below.
I only had to do steps 1-4.
Good luck. I hope it works for you as well.
Encore Crashing on Launch
1. Grab Digital Rebellion's Preference Manager (free).
2. Trash Encore's preferences.
3. Empty your Trash and restart. (If your Trash won't empty, restart, then try again.)
4. Relaunch Encore.
5. If crashing continues, grab OnyX.
6. Repair permissions, then clean system and user caches.
7.
7. Relaunch Encore.
Note: these steps should only happen once, not every time you use Encore.