Android 4.4.2 "Cannot access to camera"

I have an Acer Liquid Z500 with stock ROM (Android 4.4.2) and recently i'v been getting a "Cannot access to camera" error whenever i open ANY camera app. I tried everything:

- Clearing Cache (both camera app and gallery)
- Rebooting
- Reinstalling camera app
- Trying with other camera apps
- Hard reset

Nothing worked.