Mongrel Malformed Request error - help!

I've just migrated my system over to a new macbook.

I've been having a nightmare today trying to get the site I'm working on
to work...
All gems are in place, MySQL etc.

However - I am stuck on this error form Mongrel:

HTTP parse error, malformed request (127.0.0.1):
#<Mongrel::HttpParserError: Invalid HTTP format, parsing fails.>

The only thing it could be, I think, is we are using the SSL_Requirement
plugin.
That is redirecting to an https page and thats the last thing that
happens before mongrel shows this error.

I have never seen this before, and google searches are not showing up
much that is helpful.

If anyone has any pointers, would be much appreciated!

Thanks

Mongrel doesn't support SSL, you'll have to disable this on dev mode.