Make: target not updated until run again

[mearns . b]

I'm trying to create an "archive" (copy of the project) as follows:
The top level Makefile creates the directory and copies some stuff
into it. Then it recurses into subdirectories, and tells them to add
their own files to the directory it created. If the subdirectory
Makefiles decide to actually add anything to the directory, they touch
it to make it up to date.

Then I've got another rule to "package" the archive into a tar file,
which has the archive directory as a dependent, so it should only run
if the directory is more up to date than the tar.

The problem is, if the recursive Makefiles update the archive, but the
top level doesn't, the tar rule doesn't run, until I run the target a
second time.

I hope the Makefile below illustrates my situation. Basically, the
"archive" phony target is used to create the archive: it calls the
"my_archive" target which is like the top-level archive rule (it only
runs if the file "source" is more up to date than the my_archive dir),
and then it calls the update_my_archive, which is meant to simulate
the recursive makefiles: it updates the my_archive dir. "after-
archive" is meant to take the place of the tar file: it should run
whenever my_archive changes.

the default target is "top", which calls the "archive" target to
update the archive, and then calls after-archive. The "archive" target
always (in this case) leads to my_archive being updated, so I would
expect after-archive to have to run as well. But as I said, it only
runs if I run make twice. Below is the makefile, and following that is
a terminal transcript showing the output when I run make consecutive
times.

If anyone can explain why after-archive is considered up to date
compared to my_archive, when a previous dependency updates my_archive,
I would really appreciate it. Especially if you can also help me
figure out how to fix it.

Running GNU Make 3.81, on Fedora 9: Linux 2.6.26.5-45.fc9.i686

Thanks,
-Brian

### Makefile: ######

.PHONY:top
top: archive after-archive
        @echo Ran "top"

.PHONY:archive
archive: my_archive update_my_archive
        @echo Ran "archive"

my_archive: source
        @echo Updating my_archive because source changed
        touch my_archive

.PHONY:update_my_archive
update_my_archive:
        @echo Further modifying my_archive...
        touch my_archive

after-archive: my_archive
        @echo my_archive changed:
        touch after-archive

### End Makefile #########
##### Terminal: ##########
$ make top
Further modifying my_archive...
touch my_archive
Ran archive
my_archive changed:
touch after-archive
Ran top

$ make top
Further modifying my_archive...
touch my_archive
Ran archive
Ran top

$ make top
Further modifying my_archive...
touch my_archive
Ran archive
my_archive changed:
touch after-archive
Ran top

$ make top
Further modifying my_archive...
touch my_archive
Ran archive
Ran top