html frames and forms authentication

[psb]

I have website www.aWebsite.com. The client I made it for now wants to make
a frame wrapper on their corporate site, so my website will run in a frame
like this.

<frameset rows="134,*" cols="*" framespacing="0" frameborder="NO"
border="0">
<frame src="http://www.aWebsiteMarketing.com/top.html" name="topFrame"
frameborder="yes" scrolling="NO">
<frame src="http://www.aWebsiteMarketing.com/bottom.html"
name="mainFrame">
</frameset>

In the bottom.html there is a link to my www.aWebsite.com.

So the URL in the title bar will read http://www.aWebsiteMarketing.com, but
in the bottom frame my website
www.aWebsite.com will be showing.

my www.aWebsite.com requires a login via formsauthentication. the method:
FormsAuthentication.SetAuthCookie(customerID, RememberLogin.checked)
is not working. I don't have this problem on my WinXpsp1, but on any other
Win2k in my office.

this is probably one of the most frustrating things I have ever had to deal
with....
help, ~psb