Compiler error 'BC30456' in an ASP.NET page crops up in a deployed application that builds and runs fine in VS 2005. There's lots of noise on the net about this one, but no useful resolutions.

In my case, deleting the compiled files out of the deployed folder on the web server and re-deploying (sorry 'Publishing' in VS parlance) the web app cleared the erro.

My guess? Old compiled files were not properly deleted during the last publish causing some shit to go down. As usual when getting intermittent or seemingly random erros, "reboot" to fix.