Similar problem here, using VEP6 version 224 and with all filters exclusively from Vienna Suite (no Kontakt etc.). After successfully opening a VEP 5 project (with multiple instances) and saving it as a VEP 6 project, the reloading always gets stuck mid-way (sometimes 76%, sometimes 90%, sometimes 16%). Once, did it manage to successfully load everything. For now, I end up cancelling VEP6, restarting it and reloading the same old VEP5 project; however, I can no longer save any changes to that project, under VEP6.
Gil
Windows 10 Pro x64 build 10586.545, Intel i7-5930K 64GB, VEP 6.0.15224, Vienna suite 1.5.2049, vienna mir pro 5.4.14074, VI pro 2 2.4.14074, vienna imperial 1.1.716 and a couple of roompacks