Message Queue Insufficient Resources Error?

I am processing a local message queue and every now and then getting an "Insufficient resources to perform operation" error message when there is over 2GB RAM free.The queue is very small (often only a couple of items (if that) and never exceeds 50 items), with the items themselves being just a very basic class that consists of a filename (as a string), two integers, two booleans and one enum (i.e. very little actual data)In order to check the size of the message queue, I have a timer that ticks every 5 seconds, and when it does calls the following code:

Private Function GetQueueLength() As Integer
Dim QueueLength As Message() = ProcessQueue.GetAllMessages
Dim Length As Integer = QueueLength.Length[code].....