You might get some mileage out of turning off buffering in your CGI, and then make sure you're emitting a correct header buffer invoking your Logger. A couple of things could be going wrong inside of Logger, including permission problems trying to open the log file for append. Emitting a header first will get you post the error you're seeting, and should put you within sight of the underlying error.

Also, it's wise not to include unescaped HTML entities (e.g., "<>") in your error/warning messages.