IMO Corel has dropped the development of SVG support (they even used to have a browser plugin a few years ago) for economical reasons apparently and it is very sad. SVG has a whole bunch of possibilities unseen in other vector formats (the amazing vector blur is my prefered) and Corel could have won a lot by implementing some of the SVG possibilities into Corel Draw.
Anyway, what you are talking about (corel draw hanging when ungroupping an imported SVG) is an old and well known bug (I first encountered it in version 11 and I still see it in X4 SP1). For some unknown reason, certain groups of objects in SVG are considered as locked objects by Corel Draw. And when you ungroup such locked objects Corel just hangs (or crashes). To avoid that, use the object manager. Select the locked objects and unlock them first (get rid of all the locked objects), then ungroup them. And don't forget to save the file after each successful unlocking/ungroupping so you won have to redo the whole thing from scratch in case corel draw crashes or hangs.
I really hope that corel will rethink its point of view on SVG, it is a very interresting, promising and capable format with a bright future.