exception on destroy

Hello. I have a servant which had worked fine until recently when I added a second call from another thread. I use a client class to wrap the calling semantics and this class inits and destroys a communicator upon request, in between performing requested operations on the servant. When my 2nd thread instantiates a new instance of this class and makes its call, everything works up until destruction, when I hit the crash below. Could someone tell me where I've gone wrong here, or what might be happening? Thanks.

#0 0x00007ffff7981861 in IceInternal::Handle<IceInternal::DynamicLibraryList>::operator= (this=0x7fffe4007040, p=0x0) at ../../include/Ice/Handle.h:124
ptr = 0x7fffe4000f20
#1 0x00007ffff797e984 in IceInternal::Instance::destroy (this=0x7fffe4006f30) at Instance.cpp:1321
sync = {_mutex = @0x7fffe4006f40, _acquired = true}
serverThreadPool = {<IceUtil::HandleBase<IceInternal::ThreadPool>> = {_ptr = 0x0}, <No data fields>}
clientThreadPool = {<IceUtil::HandleBase<IceInternal::ThreadPool>> = {_ptr = 0x7fffe40077a0}, <No data fields>}
endpointHostResolver = {<IceUtil::HandleBase<IceInternal::EndpointHostResolver>> = {_ptr = 0x7fffe4001c80}, <No data fields>}
#2 0x00007ffff7910f99 in Ice::CommunicatorI::destroy (this=0x7fffe40012d0) at CommunicatorI.cpp:104
No locals.
#3 0x00007fffeeaa4b33 in X::Y::Z::HClient::disconnect (this=0x7fffebff9340) at HClient.cpp:63