I attached a IEV file which contains some hidden objects way out of range (like ObjLeft and ObjTop at -1999673).
The MouseMove ends up calling CalcDistPtObj for visible objects but it is very slow when checking those hidden objects. I had to delete those objects to make it work. You can try the IEV file attached with your Vectorial demo and see what I mean. I don't know how it's even possible to get those objects there in the first place. But let me know if you think of something that could help optimize this.