Appears to be non-yielding on Scheduler 7

In the past week we have had several instances where an SQL instance becomes unresponsive and this error appears in the server log.

Process 0:0:0 (0x14c4) Worker 0x00000000D444A1A0 appears to be non-yielding on Scheduler 7. Thread creation time: 13055521392123. Approx Thread CPU Used: kernel 0 ms, user 0 ms. Process Utilization 0%. System Idle 95%. Interval: 70062 ms.

SELECT @@VERSION

Microsoft SQL Server 2008 R2 (SP2) - 10.50.4033.0 (X64)
 Jul  9 2014 16:04:25
 Copyright (c) Microsoft Corporation
 Enterprise Edition (64-bit) on Windows NT 6.1 <X64> (Build 7601: Service Pack 1) (Hypervisor)

Can anyone provide some insight on what may be causing this issue?

Thanks