Switching between http and https popping up a login box

[Tony Wright]

Hi,

I am response.redirecting from an http to a https site, as follows:

http://mipdev05/features/MyShops/Ms...a4f12d4d-e2fd-4785-83ec-4ea2ed1ca48c&P=1&VT=G
to
https://mipdev05/features/MotorShops/MsPaymentDetails.aspx

https works fine, except that it is requiring me to log in a second
time on the redirect.
Authentication mode is set to windows.
I am only using basic authentication over SSL.

Does anyone know why it is popping up the second login box, and how do
I go about bypassing this second login box?

THanks,
Tony