Any ideas?

localhost:/usr/pkgsrc/www> uname -srm
NetBSD 3.99.15 i386
localhost:/usr/pkgsrc/www> cvs update -dPA
localhost:/usr/pkgsrc/www>

ROOT localhost:/usr/pkgsrc/www/firefox> make
...
checking for lchown... (cached) yes
checking for strerror... (cached) yes
checking for pthread_create in -lpthreads... no
checking for pthread_create in -lpthread... no
checking for pthread_create in -lc_r... no
checking for pthread_create in -lc... no
configure: error:  --with-pthreads specified for a system without pthread suppor
t 
configure: error: ./configure failed for nsprpub
*** Error code 1