When you say "Data", are you referring to Computer Data traffic? Is there both Computer and Telephone traffic on the MPLS Network? I'd take one computer/laptop and place it on the network located at your main hub. Configure it with a static iP. Take another computer/laptop and place it on the network at Node2. Configure it with a static IP as well.

Have one computer ping the other with the following DOS command:
Ping xxx.xxx.xxx.xxx -l yyy -t
(where xxx.xxx.xxx.xxx represents the static IP you are pinging. And, yyy represents how many bytes of data your packet size will be. This will provide you with a continuous ping to monitor, and allow you to control control the amount of data to get an idea of the frequency or data packet size that you are experiencing your loss.)

This should help rule out the CLEC and MPLS Provider. Hope that helps...