interactions between defclass and type specifier

[adf@ztivax.siemens.com (Angela Dappert-Farquhar)]

I have a bug I don't really understand:
We defined (defclass member ()()) and this messes up the type checks
with specifier 'member'.
(typep 'a '(member a b c)) returns NIL instead of T.

I don't know in how far PCL changed the type system or where this
interaction could occur.
Could you give me a hint? What other class names would one have to watch
out? I dont have problems with (defclass and () ()) and 
(typep 'a (and symbol t)) or something like this.

                   Angela
                   adf%ztivax.siemens.com@siemens.com