Webclient failing with SSL

I have this code in a web service:

m_webclient = New WebClient

Dim byteArray As Byte()

byteArray = m_webclient.DownloadData(url)

and this has worked for quite a while. But recently, my company added
SSL to the server and now, I get the error message, "Underlying
connection was closed. Unable to connec to remote server."

It seems as if SSL is the culprit. This code is executed from client
machines. I have the feeling I need to do something like

Dim mySP As ServicePoint =
ServicePointManager.FindServicePoint(url.ToString( ))
Dim policy As MyPolicy
ServicePointManager.CertificatePolicy() = New MyPolicy

Thanks for the heads up, but two questions:

Could you help me adjust the track? This didn't work (yet). Are there
any code snippets to cut and paste?

Also, this code is only executed from a very protected enviornment,
from behind a firewall and only after the user has logged in (via
calls through Oblix to LDAP), so it seems rather protected. Under
this circumstance, is AcceptAll still appropriate? And if not, how
would I modify that?

Ron wrote:

Thanks for the heads up, but two questions:

Could you help me adjust the track? This didn't work (yet). Are there
any code snippets to cut and paste?

Also, this code is only executed from a very protected enviornment,
from behind a firewall and only after the user has logged in (via
calls through Oblix to LDAP), so it seems rather protected. Under
this circumstance, is AcceptAll still appropriate? And if not, how
would I modify that?

Well, you have to check why the certificate is being rejected by the .NET
FCL default policy. The default policy only accepts both valid and valid but
expired certificates. So there seems to be something wrong with that
certificate in the first place. Why use such a certificate in a production
environment?

Cheers,

--
Joerg Jooss
jo*********@gmx.net

The cert is brand new and fully tested. This is the first time any
problem have arisen, so that line of reasoning is not correct.
So if you're accessing the site with a browser, it does not issue a warning?
Also, I do not understand the mechanism involved. When I force a false
return value in both methods in my Policy class, the connection is
still OK and the cert is accepted.
Weird... um... ICertifictaePolicy has only one method
CheckValidationResult(). What do you mean by "both" methods?
I have not been able to single
step through the Policy class (which just implements
ICertificatePolicy). Tthat is to say, I don't know what triggers
these functions, but it seems that the mere existence of this class
object, a non-null object value for
ServicePointManager.CertificatePolicy() is sufficient for all certs
to be automatically accepted.