After installing Microsoft Security update KB3061518, Draftsight (V1R5.1x64) clients can no longer acquire a license from the DS License Server (V6R2012x6.212.0).  Attempts to run Draftsight result in the following error message:

"Could not obtain network license activation, contact your network administrator. For standalone activation uninstall and reinstall the application."

This behavior was replicated on 3 different clients, all running Windows 7sp1 x64.  Uninstalling Microsoft Security update KB3061518 resolves the problem.