Your buffer is probably set too low.
Open Ableton Audio Control panel and adjust buffer to higher setting.
Larger sessions require a higher buffer.
If you're not monitoring audio for realtime recording, and you're only doing playback then set the buffer higher.
If you're playing virtual instruments, then set your buffer as low as your system will handle.
Also consider upgrading your storage drive to SSD or use External Thunderbolt drive for audio recording and avoid using system drive for recording audio for better performance.
Read this article on Latency and how to best adjust your system for best performance:
http://www.presonus.com/learn/technical-articles/The-Truth-About-Digital-Audio-Latency