Thanks for all the code samples. I created a console project to replicate and had no issues. The folder didn't exist to begin with on my machine it was created and log files wrote to it just fine.
I would suggest looking to see that your app has proper permissions to c:\logfiles directory.
Also another option would be to add
<appSettings>
<add key="log4net.Internal.Debug" value="true"/>
</appSettings>
To your .config and then see what debug messages are being generated by log4net.