Hashtable insert failed. Load factor too high. The most common cause is multiple threads writing to the Hashtable simultaneously.

The same code worked till yesterday and suddenly started throwing the below exception in .net 4.5

Hashtable insert failed. Load factor too high. The most common cause is multiple threads writing to the Hashtable simultaneously.
   at System.Collections.Hashtable.Insert(Object key, Object nvalue, Boolean add)
   at System.Data.DataViewSettingCollection.get_Item(DataTable table)
   at System.Data.DataView.SetDataViewManager(DataViewManager dataViewManager)
   at System.Data.DataTable.get_DefaultView()