I am not completely sure which type of ASP (Apache,VB,etc) pages you are referring to how, or more correctly when you are processing the pages, you are using HTML::Clean.
If you are using HTML::Clean with Apache::ASP there are specific guidelines in the documentation on how to it in conjunction.
If you are running it prior to compile in none Apahce::ASP environment then I would suggest looking into a using HTML::Clean at a different phase in the processing of your outgoing content.
If you post some more details about your environment I might be able to provide more help.