To identify this problem as the root cause you can use a network traffic capturing utility such as Network Monitor 3.3 (NetMon) or WireShark to record the activity between the client and server. You can then filter the frames by "MSRPC.Orphaned || MSRPC.Fault.Status == 0x1c00001a" in NetMon or "dcerpc.pkt_type == 19 or dceprc.cn_status == 0x1c00001a" in Wireshark. After filtering you should see these errors occurring around the time the error happened in the application. More specifically, you should see both an Orphan call and an error of 0x1c00001a around the time the error occurred in the faulting application.
BUG #: 262978 (Exchange Legacy)