Error: Collection was modified; enumeration may not execute

Hi,

 Every saw this error?

Uncaught exception (see the 'inner exception' below) has suspended an instance of service 'PANO042.Orchestrations.orcPANO042Type(55760f53-0d14-6615-1dad-53395a6a2d52)'.

The service instance will remain suspended until administratively resumed or terminated.
If resumed the instance will continue from its last persisted state and may re-throw the same unexpected exception.
InstanceId: 90bea657-1958-484e-9712-8dd4a1bef6e1
Shape name: Send msgNewDealRequestPAN
ShapeId: 2933710e-30ea-4371-8426-2faefa8b9c4c
Exception thrown from: segment 1, progress 68
Inner exception: Collection was modified; enumeration operation may not execute.
       
Exception type: InvalidOperationException
Source: mscorlib
Target Site: Boolean MoveNext()
The following is a stack trace that identifies the location where the exception occured

   at System.Collections.Hashtable.HashtableEnumerator.MoveNext()
   at log4net.Util.ReadOnlyPropertiesDictionary.GetObjectData(SerializationInfo info, StreamingContext context)
   at