Error: "An attempt was made to reference a token that does not exist" when impersonating by token

We have asp .net 3.5 web application running on IIS 7.
Our application has Forms Authentication with pool identity ASPNET user.
We use authenticated user and password to access a network SQL server with windows integrated security.
The token is created in form authentication page and is stored in Authentication cookie.
On every page request in Application_AuthenticateRequest the user is impersonated by LogonUser API.
After IIS restart we try to open a page from our web application.
On the first request, after logon page, we impersonate the user and get the following error:
Error code: 1008
 'An attempt was made to reference a token that does not exist'.
On every request after that we do not have that error.
The user is impersonated and can access network resources.
 
How can we fix that error?
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