(Samzenpus has confirmed this for him, too)
This is using FF 3 RC1 on OS X 10.5.2
Previewing a particular story from the Firehose results in an incomplete page: the "as it would appear" story is missing completely -- there is just white space where it would normally appear.
The "Related & Similar stories" area below the normal display area, and everything that comes below that, appear normally.
The only story on which I noticed this behavior
a) is a journal entry
b) arrived with a long title ("all other screens now appear to be covered by a gray glare")
c) has the title enclosed in quotation marks
I don't know if some combination of those things resulted in the failure to display.
(Screenshot attached, with small font size to shrink the page enough to illustrate the result.)