Mike it seems to be happening on random posts, and if you guys are not doing something yourself to "fix" specific posts, then it is going away by itself, too.
I've seen it today on short posts (say 8 lines) and long posts like the one Bill cited just above. Also with both posts made today and with older posts (again like that one).
Even when it is happening, nearby posts display correctly. Reloading the page doesn't "cure" it. While it is happening, it seems that everyone who checks the post sees the problem. Once it "fixes" itself for a given post, everyone sees the correctly displayed text again.
The text is really all still there (e.g., if you Quote or Edit you see it all), but it's just not being displayed properly in normal thread viewing.
And as best I can tell this just started happening today.