ASP.NET MVC 2 + Common.Logging + NLog = Session_Start called for each request

Question

After switching the logging library behind Common.Logging 2.1.1 from log4net to NLog 2.0 my ASP.NET MVC 2 application kept logging correctly, but it started calling the HttpApplication.Session_Start method for each request.

I'm trying to use NLog's File target with the following configuration files:

web.config

<?xml version="1.0" encoding="utf-8"?>
<configuration>
    <configSections>
        <sectionGroup name="common">
            <section
                name="logging"
                type="Common.Logging.ConfigurationSectionHandler, Common.Logging" />
        </sectionGroup>
    .
    .
    .
    <configSections>
    .
    .
    .
    <common>
        <logging>
            <factoryAdapter type="Common.Logging.NLog.NLogLoggerFactoryAdapter, Common.Logging.NLog20">
                <arg key="configType" value="FILE" />
                <arg key="configFile" value="~/NLog.config" />
            </factoryAdapter>
        </logging>
    </common>
</configuration>

NLog.config

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
    <!-- 
    See http://nlog-project.org/wiki/Configuration_file 
    for information on customizing logging rules and outputs.
    -->
    <targets async="true">
        <target
            name="f"
            xsi:type="File"
            fileName="${basedir}/bin/statistics/logs/${shortdate}.log" 
            layout="${longdate}&#009;${uppercase:${level}}&#009;${callsite}&#009;${message}"/>
    </targets>
    <rules>
        <logger name="*" minlevel="Trace" writeTo="f" />
    </rules>
</nlog>

I have already tried the following:

• Debugging the application. The ASP.NET_SessionId cookie is being sent to the server and the Session.SessionID property is not changing between requests.
• Switching back to Common.Logging - log4net to verify that the problem is related to Common.Logging - NLog. It works.
• Omitting the async="true" attribute in the targets node of the configuration file of NLog to disable the AsyncWrapper of NLog. It doesn't work.
• Using other NLog targets, tried Debugger and Database. It works.

I need to hold to the File target and I'd like to use NLog.