buildworld failure on alpha

After updating to about 0500UT, buildworld on my AS400 failed with:

--------------------------------------------------------------
>>> stage 4.2: building libraries
--------------------------------------------------------------
...
===> lib/libc
...
cc -O -pipe -mcpu=ev45 -mieee -I/home/src5/lib/libc/include -I/home/src5/lib/libc/../../include -I/home/src5/lib/libc/alpha -D__DBINTERFACE_PRIVATE -I/home/src5/lib/libc/../../contrib/gdtoa -DINET6 -I/home/obj/home/src5/lib/libc -DPOSIX_MISTAKE -I/home/src5/lib/libc/locale -DBROKEN_DES -DPORTMAP -DDES_BUILTIN -I/home/src5/lib/libc/rpc -DYP -DHESIOD -Wsystem-headers -Werror -Wall -Wno-format-y2k -Wno-uninitialized -c /home/src5/lib/libc/net/ns_ttl.c
cc -O -pipe -mcpu=ev45 -mieee -I/home/src5/lib/libc/include -I/home/src5/lib/libc/../../include -I/home/src5/lib/libc/alpha -D__DBINTERFACE_PRIVATE -I/home/src5/lib/libc/../../contrib/gdtoa -DINET6 -I/home/obj/home/src5/lib/libc -DPOSIX_MISTAKE -I/home/src5/lib/libc/locale -DBROKEN_DES -DPORTMAP -DDES_BUILTIN -I/home/src5/lib/libc/rpc -DYP -DHESIOD -Wsystem-headers -Werror -Wall -Wno-format-y2k -Wno-uninitialized -c /home/src5/lib/libc/net/nsdispatch.c
mv y.tab.h nsparser.h
mv: y.tab.h: No such file or directory
*** Error code 1

Stop in /home/src5/lib/libc.
*** Error code 1

Anyone else seen this?

I've deleted /usr/obj, updated and am trying again but it will take
some time to know if the problem has gone away.

-- 
Peter Jeremy