Session lost in customErrors, defaultRedirect

[Guest]

Hi

I'm just testing some web stuff and created a errorpage to display nice messages to all users
My page that raises the error uses Server.GetLatestError to get the error and store in a session variable
My web.config file has a customErrors-tag and uses defaultRedirect to redirect to my errors page

It works fine, the error is caught on my page, session variable is set but on the errorpage the session is empty
Why is a new session created and how can I fix this

If I use Server.Transfer to go to my errorpage (instead of defaultRedirect), the session is intact

Any suggestions

Thanks
Markus