Works here. What kind of error message are you getting?
$ cat test | gpg --clearsign -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi Marc! -----BEGIN PGP SIGNATURE----- iHUEARYKAB0WIQQzCL4DU6GJknHiY4x4Qe+41iriQQUCaY3YCAAKCRB4Qe+41iri QfVjAQDDW1RvJpG0mYBafUK702QXAA++Mw2TiIC+2xWp5czn1AEA48ZisFL9wrid Kt1Mv8CJWJBTBbD+V1iRaVjQ9JCWPQc= =RR7P -----END PGP SIGNATURE----- (that's from a throw-away key for testing on sid)
