Recently did an HP-update and dual-boot broke

I have an HP Pavilion dv6 laptop. I set it up for dual boot between the
stock Windows 7 (resized with parted magic disk) and Ubuntu 11.04 (each OS
on a partition on the internal drive). This worked great for months.

A couple of days ago HP's support assistant installed one or more software
updates to the windows side (possibly related to power management.) After
that, Windows fails to boot (Ubuntu is fine). It gets to the "Starting
Windows" splash screen. You see the text, but the animated RGBY logo never
appears. And it sits there ad-infinitum.

Using HP's recover disks and their recovery manager software, I tried to
rollback to various restore points without any luck. Tried a few other
fixes (again without luck), and finally did the nuclear option: a full
return to factory default (complete with a drive reformat.) (I backed up,
so data loss isn't an issue.)

After that, I update windows (over and over and over), install and update
Norton 360, AND install all of the HP updates (which presumably includes
the update that started the headache in the first place.) After all of
that, windows still boots and runs fine.

I boot off of the Parted Magic CD and shrink the windows partition, and
create a couple of partitions that will eventually be used by Ubuntu.
Reboot in to windows without any issues (it checks the disk for
consistency, but that is to be expected.)

But when I install Ubuntu 11.04 dual-boot again, Windows stops booting.
(Although Ubuntu is happy as a clam.)

So I am in a situation where I can have the laptop set up to run either
Windows, or Ubuntu. But it can not be set up to do both. At least not on
the same drive. If I had a spare bootable USB drive I would try installing
Ubuntu on that.

My best (wild) guess is some sort of incompatibility between Grub2 and
whatever HP's updater did. But my understanding of grub is tenuous at best.

I dread trying to talk to HP about Linux; so I thought I would check here
first. Is anyone else running dual-boot on an HP laptop? Have you seen
this? Is there a known fix? Any other wild ideas?

Thanks.