Only one update at a time?

ok, this is annoying... I did search for this, but it's not a really easy
topic to search for, given the possible search words.

I reinstalled XP Pro a couple weeks ago, but the Automatic Updates (AND on
the Windows Update site) will only let me install one update at a time. I
know that some updates must be installed before others, but it'll only even
show one update as being available. As soon as it's installed, another
update pops up. And so on, and so forth. And, no, I don't have any updates
hidden.

With Windows 2000, I could just let the Automatic Updates program run and
download updates to its hearts content and let me install them when I got
around to it. But, even if I have the XP auto updater set to download and
install automatically at a certain time, it'll still only do one update.

I'm downloading the single-file installer for SP2 right now, but I'd sure
like to know what caused this problem, incase it happens again. Any ideas?