Ableton has updated Live to v5.0.3.

Improvements:

• [OS X] Better support for hot (un)plugging of audio interfaces.
• [Win] Added a preference to enable the System file cache for reading files from hard disk.
• Stop clips and clips with quantization set to 'global' are fired unquantized in follow actions.
• A clip stop action based on follow action is always unquantized.
• Improved GUI performance when any a Mackie Control device is selected in Live's MIDI preferences.
• Improved GUI performance when select a scene or a track in the Session view.
• Reduced memory usage. Depending on how many clips and how many different physical audio files are used within a set Live could need up to 25% less memory.
• Mackie Control Support:
  • Holding down shift while pressing play will do Pause or Continue now.
  • Bank switches will now never align the tracks to the last strip, but always wrap by the number of available strips (8, when using only the main Mackie without any extensions).
  • Support for the "ProjectMix IO" hardware from M-Audio.
• Improved MIDI input timing accuracy.
• When pressing a keyboard key, which is assigned to the Computer MIDI Keyboard and the RemoteMapper, the keyboard and key-learn mode buttons will flash for a short time in key-learn color to indicate the conflict.
• Better GUI performance when firing a scene via KEY remote and "Select on Launch" is enabled.
• Shift + Space also does a Song stop.
• Improved warper performance when no interpolation is required.

Numerous bugs were also fixed, a complete list of which can be viewed in Ableton's support forum.