ah getting closer...
found this in make.log in gr-usrp-0.5cvs*************.tar.gz
*** Warning: libtool could not satisfy all declared inter-library
*** dependencies of module _usrp0. Therefore, libtool will create
*** a static module, that should work as long as the dlopening
*** application is linked with the -dlopen flag.
ar cru .libs/_usrp0.a .libs/usrp0.o .libs/usrp0_sink_c.o .libs/usrp0_source_c.o
ranlib .libs/_usrp0.a
creating _usrp0.la
(cd .libs && rm -f _usrp0.la && ln -s ../_usrp0.la _usrp0.la)
-----------------------------------------------
meaning that the _usrp0.dll couldn't be generated. not sure how to
make it myself, will have a play about again. renaming the libusrp0
dll doesn't do the trick unfortunatly.