LDP can authenticate with SSL, so why is my app returning 403

I have 3 vms.  VM1 - is in Domain A.  VM2 & VM3 are in Domain B.

vm1 is running ldp.exe

vm2 is running an instance of AD LDS as a proxy to AD

vm3 is running AD

I can use ldp on vm1 to do a simple bind using ssl by first connecting to vm2 (ad lds)

Now I have a browser running on vm1 that connects to a server on the same box (vm1) and that server is supposed to authenticate with the creds I enter in my browser and authenticating using the same vm2 and vm3 that ldp was successful with.  However I get a 403 error?  Why would this happen, if I can run ldp successfully from the same client box (vm1) that is supposed to interact with vm2 and vm3?

Note that my server is running on vm1 and listening on port 8443.

Thanks.

leo