After uploading the new asp.net version of HowToDoThings.com various people noticed that they were often seeing the following error messages instead of the intended page
[No relevant source lines]
Eventually I was able to discover that this was because I had uploaded signed assemblies to my BIN folder on the server, apparently this is not allowed.
The solution is to either unsign all of your assemblies, or install signed assemblies into the GAC. I have also read that it if you build your project twice before uploading then this restriction does not apply, but I only had limited success using this second approach.