Cracked Transmission - WTF?!

[wmc2004aug at bellsouth.net]

Welp, I'm in the process of dropping the tranny out of our NX.  You
might recall I complained last week it was "falling apart".

All this started when I found a large puddle of gear oil under it Wed
last week.  I hoped it was just a seal.  But got the rear mount
removed, and it's the dreaded Cracked Transmission Syndrome.

If I was beating the crap out of this car, like my old black one, I
wouldn't be surprised.  But this one has been Lisa's car for nearly
12 years;  even with 195K, it's been driven pretty tamely.  It
doesn't have enough power or clutch to generate the wheel-hop usually
blamed for cracks.

Any idea what could have caused it?!

    -Wayne    '93 SE-R / '93 NK2k / '90 Miata