I have had this problem as well with 7.9.1.
Don't know if there is an automated method to sort it out (hopefully someone from Mentor can provide details if there is)
The way I have resolved the problem, is within the schematic click on the properites of the part/symbol and it will list the cell name proporty. Just delete this value (leave the property).
Then you will be able to package your design.
Tip - When you do the project integraption within the pcb, click on additional options and un-select the Back annotate cell names to schematic option.
This works in 7.9.1 so think it is about the same in VX.