I was debugging some issues at work and we ended up discovering a compatibility issues with some the dll's. These issues were discovered primarily by looking at the Fusion logs. The fuslogvw.exe provides quick and easy access to the logs which in turn describe a variety of issues, however, I have found that binding errors are most common and easily determined.

Fusion logs describe the probing paths used to find compatible dll's and the success or failure of the search.

LOG: Attempting download of new URL file:///C:/Program Files/RssBandit/en-US/BlogExtension.Delicious.resources.DLL.
LOG: Attempting download of new URL file:///C:/Program Files/RssBandit/en-US/BlogExtension.Delicious.resources/BlogExtension.Delicious.resources.DLL.
LOG: Attempting download of new URL file:///C:/Program Files/RssBandit/plugins/en-US/BlogExtension.Delicious.resources.DLL.
LOG: Attempting download of new URL file:///C:/Program Files/RssBandit/plugins/en-US/BlogExtension.Delicious.resources/BlogExtension.Delicious.resources.DLL.
LOG: Attempting download of new URL file:///C:/Program Files/RssBandit/en-US/BlogExtension.Delicious.resources.EXE.
LOG: Attempting download of new URL file:///C:/Program Files/RssBandit/en-US/BlogExtension.Delicious.resources/BlogExtension.Delicious.resources.EXE.
LOG: Attempting download of new URL file:///C:/Program Files/RssBandit/plugins/en-US/BlogExtension.Delicious.resources.EXE.
LOG: Attempting download of new URL file:///C:/Program Files/RssBandit/plugins/en-US/BlogExtension.Delicious.resources/BlogExtension.Delicious.resources.EXE.
LOG: All probing URLs attempted and failed.

The following registry location [HKLM\Software\Microsoft\Fusion\LogPath] will show you where the raw logs are stored. If you use Visual Studio.NET you will notice quite a few of your own applications have orphaned fusion logs as well as whatever .NET applications you use.

If things are going drastically wrong with a complicated multi assembly installation, then take the time to look at the fusion log files.

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