Message Queue Error: "QueueExists"

I get following error (tranlated from ger to eng):

"Eventqueue action error with 'MessageQueueErrorCode' QueueExists for the Queue 'a37f912a-9c...'."

What I do:

I have a state machine workflow with 4 states. At the point where this error happens I am in the RunningState. There I have an EventHandlingActivity which listens for a certain event. If this event happens I need to check 2 variables After a successfull check I add a delay activity (with a EventHandlingActivity) to the current state (executing state). This seems to work (my code is executed) but I cannot monitor the addition of the delay activity, because I gets terminated. Event the dynamic update code gests executed.

Is it a problem that my workflow tries to change the current state Could I solve this problem by adding another state in which my workflow stays while the changes to the other state take place

How can I check if the above mentioned Queue already exists

Thanks

Klaus