Please install/update to Library API 7.x-2.0 or later before updating to this version.
If you need the form support stay with version 7.x-1.4.
Major changes in 7.x-2.x:
- Removal of form support.
- Dependency on Library API, version 7.x-2.0 or later.
- A a new plain style that works well with photos.
For all changes please see the beta 2.x releases at Releases for Colorbox.