Is Windows XP getting less bulletproof?

Over the last year or so I’ve noticed that misbehaving apps like Musicmatch, and some really big pdfs, quicktime movies and software DVD players (to name a few) can lock Windows XP up so solid that hardware reboot is the only way out. A few years ago when XP first came out there almost nothng that I couldn’t kill using the task manager. Why are the latest apps much more adept at locking up XP and resistant to being terminated than the old ones?

There are really at least four flavors of XP to consider:

A freshly installed or imaged PC that’s not been updated (And is it SR1 or SR2?)
A freshly installed and updated PC (This will be SR2 and IE7)
An old unpatched install
An old but up to date install (It’ll be SR2, and probably IE7)

Which is getting clobbered by these apps? Regardless of patches, the older installations are very likely to have bits and pieces of things (invalid keys, half-uninstalled things, etc) scattered about in the Registry that other apps, or the system itself might trip over.