We recently deployed VRF groups on our core switches and there are a few key changes to troubleshooting/configuration.
Standard way: ping
w/ VRFs: ping vrf NAME (where NAME is the name of the vrf group)

Standard way: traceroute
w/ VRFs: traceroute /vrf NAME

If you are trying to make a connection to a destination that resides in a VRF from the core switches you will most likely have to include some sort of VRF tagging.  This even applies to services like RADIUS, NTP, DHCP Relay, and TACACS.