Wife's R51 won't update . . .

[Wayne]

I have a ThinkCentre, home built, Compaq, and three ThinkPads, all running XP Pro SP3. They will all get the MS updates. Except the wife's. When I run the MS Update it goes to the site, goes through the gyrations of checking, and always comes back with the no updates needed with the exception of Defender. But I have missed the last three months of the Update Tuesday updates. The others work perfectly. Since it gets the Defender updates I know it's connecting. But the other Critical and such will not show up.

Any thoughts?