When I performed an FTP install of rawhide a few days ago,
the following packages hung either before or after
installing due to the pre/post-install scripts trying to
call groupadd or useradd, and those processes locking (I
solved the problem each time by backing up the script in
/mnt/var/tmp/ to be run later and using /proc to get the
address of the command to kill):

linuxconf, postgresql, slocate, squid

Sendmail also died but because of "newaliases" which locked
for its script.