Log4Net.Error throws VerificationException - Operation could destabilize the runtime

We are running into this issue when we log errors/fatal message using log4net.

> System.Security.VerificationException: Operation could destabilize the
> runtime. at log4net.Core.LogImpl.Fatal(Object message, Exception
> exception)

Strangely this happens only when we log as Error/Fatal, Info and Debug messages log perfectly fine. Because of this exception, the real exceptions are getting masked and its making it very hard for us to debug in deployed environments.

I have tried searching online but to no avail. Any help is appreciated.

Environment details:

IIS 7.5 / Win 2008 R2
.Net 4.0
MVC3 and WCF applications

Here is the logging configuration-

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net"/>
</configSections>
<log4net>
<appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
<file value="C:\Logs\ApplicationServices.log" />
<staticLogFileName value="true" />
<appendToFile value="true" />
<datePattern value="yyyyMMdd" />
<rollingStyle value="Date" />
<filter type="log4net.Filter.LevelRangeFilter">
<acceptOnMatch value="true" />
<levelMin value="DEBUG" />
<levelMax value="FATAL" />
</filter>
<layout type="log4net.Layout.PatternLayout">
<conversionPattern value="${COMPUTERNAME} %date %-5level %class.%method - %message%newline"/>
</layout>
</appender>
<root>
<level value="DEBUG"/>
<appender-ref ref="RollingLogFileAppender" />
</root>
</log4net>
</configuration>