Server 2008 AD issue across forest trust with Server 2003 R2 AD

[dhess1013]

We have 2 seperate Domains with a forest level trust. On one Domain we have 3 Server 2003 R2 DC's. On the other Domain we have 1 Server 2008 DC. The trust works just fine as I can browse each Domain from the other, however I need to add user access to the shares on each Domain... I upgraded the 2003 R2 AD Schema to the 2008 AD Schema using adprep /forestprep, so that all the AD's have the same Schema. When I try to add a user to a share, I am able to change the Location to the other Domain, but my problem is that I cannot add a user to any shares from one Domain to the other Domain and vice-versa. Any advice would be appreciated.