Ruby 1.9 introduced the new syntax for hashes:

{key1: value1, key2: value2}

which is synonymous to {:key1 => value1, :key2 => value2}

The latest ruby-mode highlights the keywords in the new-style hashes 
properly, but fails to account for the case when the symbol's name is an 
otherwise reserved keyword. Examples:

link_to("root", root_path, class: "pink")

before_filter :do_stuff, if: :not_busy?

announce("The end is near!", end: "2012-12-31")

In all examples, the symbol (class, if, end) is being highlighted as a 
reserved keyword, and the indentation becomes broken on all lines below it.

There's a similar bug on the Ruby bug tracker:
http://bugs.ruby-lang.org/issues/5140

See attachment for the patch.