Reason mapping lost when opening project

Hi all,

Having a small problem with Reason 4.1 and Nuendo 5.5

When assigning a Nuendo midi track to a Reason sounds module all if fine, but when I reopen the sessions the next day it loses all the mapping info. I then have to go back through the midi channels in Nuendo and re-assign them to the corresponding Reason module. In past versions of Nuendo when I open the projects the midi channels are auto assigned to the modules??? weird!

Anyone else experiencing this or know how to fix it?

Thx

Mac 2.2 quad Xeon
OSX 10.6.8
Nuendo 5.5
Reason 4.4
Motu V4HD
Euphonix artist series - Mc Control Mc Mix MC transport