Hi,

Under what conditions does an activity expire, apaart from it being terminated?

One of the client events in an activity is expired. It actually calls a web service invoking the database and the web service has failed creating an expection.
Is there a possibility to reactivate this expired activity or could the workflow be taken back to a previous activity and restart the workflow? 
Please suggest any other alternatives for the workflow to continue which seems stuck owing to the expiration of an activity within?