The VNC issue is resolved as of now. Please see below for details:
Cause
Issues with network infrastructure impacted ability connect to the AD server.
Impact
New or existing VNC sessions were unable to start/reconnect.
Duration
3:28pm - 5:21pm
Mitigation/Resolution
One of the redundant uplinks was accumulating errors and discards. The bad uplink was removed. Network team is continuing to investigate the issue.