@mochman and @BeLuGe can you tell us what are the versions you are using :
Raspbian Jessie or Wheezy, which version of nodes, npm … ?
From where are you running npm start (local, ssh) using sudo or not ?
I have the same issue as @BeLuGe and I would like to debug/understand what’s is the problem.
I already red it could be a nodejs version issue (compiling vs running version)
So guys tell us what are your configuration

Here is mine :
Rpi 3 updated firmware with rpi-update
Raspbian Jessie last version (apt-get update && upgrade && dist-upgrade)
Nodejs last version 6.5.0 ARM version (not sure if it’s 64 bit or 32 bit) from https://nodejs.org
Then install of MM and packages
MM is working fine until I add MMM-Swipe module configuration then got same error message about
Error: Module version mismatch. Expected 49, got 48.

Hope we will find the solution …