Unless your code use some PM syntax assembler lines, there's no good reason why it shouldn't compile with MPASM except Config/Device line... or the MPASM path is wrong and point to another older version. So you should check if the path is actually set to the newer version. Here it's located at C:\Program Files\Microchip\MPASM Suite

Just post your code here, maybe someone could help you to point some mistakes or give you some hints. In case you can't post it in public for some NDA reasons, you can still send it to me in my e-mail address.