pax error: File name too long for ustar

I am trying to make a tar archive with pax.  The command I am using is
the following

    /bin/pax -w -v -x ustar -z -s "|^\\.|./probability|" .) > archive.tar.gz

I get the following error message:

  ./probability/structstd_1_1numeric__limits_3_01boost_1_1probabilities_1_1likelihood_3_01boost_1_1probabilities_1_1linear__domain_00_01Value_01_4_01_4.html
  pax: File name too long for ustar ./probability/structstd_1_1numeric__limits_3_01boost_1_1probabilities_1_1likelihood_3_01boost_1_1probabilities_1_1linear__domain_00_01Value_01_4_01_4.html

The pax man page has the following to say about the ustar format:

           ustar    The extended tar interchange format specified in the IEEE
                    Std 1003.2 (``POSIX.2'') standard.  The default blocksize
                    for this format is 10240 bytes.  Pathnames stored by this
                    format must be 250 characters or less in length.

The above file name is not greater than 250 characters by my count.

Can anyone identify the problem here?  Thanks for your help.

Cheers,
Brook