We have recently replaced an old OPC interface to a KepWare server with the Prosys UA Java client. The main purpose was to avoid DCOM and to be compatible with Windows 64 bit servers. The application has since then crashed 1-3 times a day. Java dies suddenly without any stack dump or other error messages and we have not been able to find a pattern of when it happens and what triggers the crash, it happens after 5 minuts or after 5 hours. It does not look like a resource problem – there is no memory leakage. The application is multithreaded, each thread has its own instance of UaClient (also tried with one shared instance with synchronized access, but this seems more unstable). The client is created as:

client = new UaClient(uri);
client.setSecurityMode(SecurityMode.NONE);
client.connect();
client.setAutoReconnect(true);

Read and write access are very simple:
val = client.readValue(NodeId.parseNodeId(item));
and
client.writeValue(NodeId.parseNodeId(item), new UnsignedByte(value));

It is Java 7.0.51, Windows Server 2008/64bit.
Has anybody had similar experiences?