I am doing some development on my local machine using VS 2010 and running my dev code in Cassini, I also have taken a copy of the same code and deployed it to c:\\mp and set
The issue is with the cookie, because the cookie keep the logged confirmation.
Changing the name of your cookie on web.config is probably solve your issue. So setup the name and the domain according to the two diferent logins, using 2 different cookie suffix names.
<authentication mode="Forms">
<forms ... name=".CookieSuffix" domain="yoururl.com" ... />
</authentication>
You'll need to explicitly set the names for some cookies in your web.config. Here's some of the typically required ones :
1) authentication cookie
<authentication mode="Forms">
<forms name=".ASPXAUTH_YourAppName" ...
2) role manager cookie
<roleManager cacheRolesInCookie="true" cookieName=".ASPXROLES_YourAppName" ..
3) session state cookie
<sessionState cookieName="ASP.NET_SessionId_YourAppName" ...
I tack on a unique suffix to the default cookie name for different applications. e.g. in the above, replace "YourAppName" with something unique for your different app instances.