When you install dasBlog in the root of a web server as I have, it's web.config is inherited by all lower level applications. This is a problem for nGalley as the dasBlog config has <httpModules> loaded. You can unload them by adding the following to the nGallery web.config:

<httpModules>
  <remove name="ControlImageModule" />
  <remove name="UrlMapperModule" />
  <remove name="CompressionModule" />
</httpModules>

This doesn't quite solve the problem though as the nGallery application still needs to be able to load the dasBlog assemblies in order to remove the <httpModules> so add the dasBlog assemblies to the nGallery bin folder.

I'm not too sure why you still need the assemblies in the nGallery bin directory - maybe someone can enlighten me.