What package is responsible for the functionality of the keyboard

I'm attempting to forward this bug report in Launchpad to the appropriate project, but I'm not sure which one that is. The issue is with the user's keyboard, and the issue is that some multi-key keyboard shortcuts are not being recognised if the user presses them in a certain order.

This seems to be the result of a known bug (I can reproduce the behavior from the report you linked to). Its description contains all the necessary information to find a proposed patch, which probably will find its way into Ubuntu 11.04 (see comment #119 from Bryce Harrington).

As a workaround, you could change the keybinding to switch layouts via:

• System > Preferences > Keyboard , then
• Layouts > Other Options... > Layout Switching > Key(s) to change layout :
  
  

The answer posted by htorque helped with the particular bug report, and the bug report linked to by htorque reveals that xorg-server is responsible for keyboard input, along with the management of most other input devices. More information on the X Window System can be found at it's Wikipedia article.