The bond rates are very, very close (or were as a of a month or two ago), so I doubt expecting Spain to be bailed out but not Ireland explains it. Not to mention that there were some hard fought EU related battles in Ireland, so failing to bail them out would mean no more progress for the EU there (and while the EMU may collapse or change radically, I expect the EU to survive).

As a side note, unlike Greece and some of the others Spain was not actually misbehaving (i.e. the government regarding irresponsible debt). I think the housing bubble burst bit them hard like it did in many countries (i.e. private sector screwed everything up like here in the US [excluding failures of regulatory agencies to do their job]).

Update: Fixed grammar in first sentence