Ruling Question: Can you stop a spell by untapping the land used for it?

Hello all.

I've got a question regarding the land tapped to cast a spell.

Say my opponent has 5 lands out, and uses 3 of them to summon card X.
Now, I use a Twiddle (or any other permanent tap/untap card), and untap
one of the lands.

Does the spell fizzle out?  The land originally tapped to cast it has
now become insufficient.  Can the opponent re-tap the land?

Further to this, say I play a Creeping Mold on one of the lands; the
land is now destroyed.  Can the opponent tap one of the remaining two
lands to compensate for the destroyed mana?

This was a point of debate in my last game, and we decided to let it
slide (i.e., the spell was still 'good') until I asked here. :D

Cheers,
Patrick

Cheers,
Patrick

-- 
tendim
remove all capitals from eMail address for replies