Webservice for PPC Error using .Net 2.0

[John]

I have developed a simple Webservice for a Pocket PC on .Net 2.0
I have succesfully connected and used the Webservice with one Pocket PC, but
when I deploy my solution to a second/third Pocket PC and try to connect with
all the same parameters I get an error (actually two different errors):
1. "Could not establish secure channel for SSL/TSL"
or
2. "Could not establish trust relation with remote server"

The stack shows that it fails in :
System.Net.HttpWebRequest.finishGetResponse()

This is the code I use in the local webservice client constructor:

string serverUrl = AppSettings.GetValue("ServerUrl");
this.Url = serverUrl + "/Service/Service.asmx";
string userID = AppSettings.GetValue("UserID");
string password = AppSettings.GetValue("Password");
string domain = AppSettings.GetValue("Domain");

CredentialCache myCache = new CredentialCache();
myCache.Add(new Uri(this.Url), "Basic", new
System.Net.NetworkCredential(userID, password, domain));
myCache.Add(new Uri(this.Url), "Digest", new System.Net.NetworkCredential
(userID, password, domain));
this.Credentials = myCache;

Hope anyone can help...

John