We found similar problems running OPC DA 32 bit with Ignition 64 and Java 64. In 64 bit environments I suggest if you are going to use OPC DA you are better of using Ignition 32. with Java 32.
OPC DA and DCOM are hard to set up with 64 bit environments and the applications become quite unstable.
Even the OPV quick client becomes unstable, it hangs up the configurator and the ignition server.
Even Microsoft states that Office 32 should be used in 64 bit environments, concurrent applications run better.