Check the Application event viewer log on the Epicor server for out of memory errors like this one:
WebHost failed to process a request.
Sender Information: System.ServiceModel.ServiceHostingEnvironment+HostingManager/35988427
Exception: System.ServiceModel.ServiceActivationException: The service ‘/E10DemoDB/Ice/BO/ReportMonitor.svc’ cannot be activated due to an exception during compilation. The exception message is: Memory gates checking failed because the free memory (858288128 bytes) is less than 5% of total memory. As a result, the service will not be available for incoming requests. To resolve this, either reduce the load on the machine or adjust the value of minFreeMemoryPercentageToActivateService on the serviceHostingEnvironment config element… —>
EDIT: if it is that error, you can have Windows ignore the low memory condition via this post: