I just installed some updates from MSFT, my computer said that it needed to restart, but it shut down completely and didn't restart, pushed the power buttin and it said it couldn't read the disk, put the installtion disk in the CD, resarted the machine, let it install the files, like if it was going to instal Windows, picked the language and time, then at the install page in the bottom left it has a repair check box, the next page has the options for if you made a backup,( I haven't), so I picked next at the bottom, then was given a list of options, so I picked repairing the startup, and let it run, after a few minutes, it started with the regular boot screen and opened to the UAC, picked mine and logged in, everything seems fine, so consider this a warning, Win 7 may have a update problem, and at least in my case it was repairable
I should point out that this is a completely useless account of a failed update (99% chance this had something to do with your machine specifically, rather than the update itself) without posting the KB article number(s) that you installed when this problem occurred.
I should also point out that every time Microsoft releases a new round of patches, it is literally impossible to test them on every single hardware configuration out there, with every possible software configuration running on top of those. There are literally infinite possibilities. I really am surprised things like what you described don't happen more often.