Thank you for providing feedback on this Release Candidate version! There was a tagging error in version 1.2.0.rc1. Unfortunately there is no way to remove or replace a problematic version on WordPress.org, therefore we released version 1.2.0.rc2 immediately afterwards. Can you please upgrade to 1.2.0.rc2 and let me know if the error persists? If it does, please let me know what is your PHP version (e.g. 5.5.15) and your operating system (e.g. Linux, Windows, Mac OS X and so on).
We have found out what the issue is: some filenames are in lowercase when their first letter should be uppercase. We are preparing a new release (1.2.0.rc3) which will address this issue.
WordPress.org uses a Subversion repository to provision the update packages to the plugins hosted in the Plugins repository. Unfortunately, this makes it impossible for us to test the packaging before actually releasing a version. On top of that, there is no feedback whether filenames are committed in the correct case or not. On the bright side, this version is the last one where a filename case change is required so we don’t expect this near-impossible to prevent issue to occur again.
