Magento Connect Errors - Udates from 1.9.1.0 to 1.9.1.1

I am trying to upgrade a number of extensions from 1.9.1.0 to 1.9.1.1 in the Magento Connect Manager, however these persistently fail. The main extension I want to upgrade is Mage_Core_Modules, but despite showing the upgrade as being available, I get the following error:

Mage_Core_Modules 1.9.1.0 (stable) 1.9.1.1 (1.9.1.0)
CONNECT ERROR: Package community/Mage_Core_Modules failed: No releases for 'Mage_Core_Modules', skipping

And for other modules the same or a conflict error with Mage_Core_Modules 1.9.1.0:

• Interface_Adminhtml_Default 1.9.1.0 (stable) 1.9.1.1 (1.9.1.0)
  CONNECT ERROR: Package community/Interface_Adminhtml_Default failed: No releases for 'Interface_Adminhtml_Default', skipping
• Interface_Frontend_Default 1.9.1.0 (stable) 1.9.1.1 (1.9.1.0)
  CONNECT ERROR: Package community/Interface_Frontend_Default failed: No releases for 'Interface_Frontend_Default', skipping
• Lib_Mage 1.9.1.0 (stable) 1.9.1.1 (1.9.1.0)
  CONNECT ERROR: Package community/Lib_Mage 1.9.1.1 conflicts with: community/Mage_Core_Modules 1.9.1.0
• Mage_Compiler 1.9.1.0 (stable) 1.9.1.1 (1.9.1.0)
  CONNECT ERROR: Package community/Lib_Mage 1.9.1.1 conflicts with: community/Mage_Core_Modules 1.9.1.0
• Mage_Core_Adminhtml 1.9.1.0 (stable) 1.9.1.1 (1.9.1.0)
  CONNECT ERROR: Package community/Mage_Core_Adminhtml failed: No releases for 'Mage_Core_Adminhtml', skipping
• Mage_Downloader 1.9.1.0 (stable) 1.9.1.1 (1.9.1.0)
  CONNECT ERROR: Package community/Mage_Downloader failed: No releases for 'Mage_Downloader', skipping
• Magento_Mobile 1.9.1.0 (stable) 1.9.1.1 (1.9.1.0)
  CONNECT ERROR: Package community/Magento_Mobile failed: No releases for 'Magento_Mobile', skipping

I have cleared caches, switched https on/off in the config, logged in/out, turned maintenance on/off etc.. but no simple tries have worked - all suggestions very welcome. I am wary of updating via ftp but if there is no other option, maybe this is possible.

Am I missing something simple?

I had the same problem. I have partially solved this problem by running a reinstall of all 1.9.1.1 components that installed successfully and setting the components you listed above to upgrade at the same time. This finally upgraded the components together. However, Magento_Mobile 1.9.1.0 package is still getting this error regardless if I try to set the previous components to reinstall.