That's because Ryouga thinks of her as a guy. Though he did nose bleed when
Ranma showed him her clevage... That's why he's not affected by onna Ranma,
either. If he thinks the person's a guy, then they're a guy to him... And
Ranma is Ryouga's most hated enemy, so how could he think of having a nose
bleed when this is the person he hates? Hate takes over from embarassment
there...

EXCUSE ME!??!?! Ryouga thinks of Ukyou as a GUY?!?! In the dress she was
wearing in the second movie!??!

Since when did Ukyou ever dress like that in the manga? I'd like to see
that page, if you'd kindly point it out to me...

 [Aaron is curled up into a ball whimpering]
 Kendra: [poking him in the ribs with a finger] Really put your foot in it
this time, didn't ya?
 Aaron: *whine* *whimper*
 Kendra: oh dear...

Kun-chan giggles.

Fine, laugh at my little breakdown *sniffle* I know when I'm not loved
*sniff* *sniff*
 Kendra: oh no...
*BBBBBBBBBWWWWWWWWWWWWWWWWWAAAAAAAAAAAAAAAA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!*
 Kendra: [barely heard over the bawling] My predacessor told me I should
select a weapon to use for times like this!

Kun-chan patpats, instead, and tries not to laugh. ^_^

Kun-chan...