Problems with different versions of log4net

Hello,

I've got an existing Class Library with a lot of functionality and business logic, that I'm trying to integrate with a clean install of Umbraco 6.0.

Unfortunately, some of the external dlls that we're using are relying on log4net version 1.2.10.0 and Umbraco 6.0 uses log4net version 1.2.11.0...

I tried the simple fix of replacing the dlls. When replacing the log4net.dll in the Umbraco/bin dir with the old version, we get this error when starting up the website:

"Could not load file or assembly 'log4net, Version=1.2.11.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies."

When using the new version of log4net Umbraco works, but the page calling a method in our class library will fail with:

"Could not load file or assembly 'log4net, Version=1.2.10.0, Culture=neutral, PublicKeyToken=be58efc3b934219b' or one of its dependencies."

I've tried this solution: http://stackoverflow.com/questions/2460542/using-different-versions-of-the-same-assembly-in-the-same-folder

But for some reason this doesn't work for me. Is there another way of doing the same when running a website or am I missing something?

Does anybody have any tips on this or have had a similar problem?

Thanks,

Mikkel