I have seen other tabs of this on Ultimate Guitar and I must say, they aren't quite 
accurate, sorry...
I have figured this song out for myself and thought I would show it to you.
(These are the chords and keyboard/vocal melodies).
I have also arranged a solo acoustic version of this song that involves playing both the melody
and the chords on acoustic guitar (capo 3). If you want me to post the tab of this,
simply email me.

hey_sac@hotmail.com

Crystal Castles
Untrust Us

Standard Tuning (EADGBE)*
*(The tuning is strange - it is like half a half step so I just play it in standard tuning)
Key: G minor/Bb major

Chords:
Intro/Part A(s)

4|                   .|
4| Gm | Gm | Gm | Gm .|  x4

Verse(s)/Part B(s)

4|                     .|
4| Gm | Eb | Bb | Bb/A .|  x ...

Main Melody:
Intro/Part A(s)
(Listen to the song for more accurate rhythms)

(Gm)      (Gm)

E|-6-------|---------- |
B|--8-8-8--|-6-8-8-8-- |          (I like to add a little vibrato
G|---------|----------.|               or play with a slide)
D|---------|----------.|   x8
A|---------|---------- |
E|---------|---------- |

Verse/Part B(s)
(Listen to the song for more accurate rhythms)

(Gm)        (Eb)        (Bb)        (Bb/A)

E|-----------|-----------|-6---6-----|-6-6-------|
B|-8---------|-----------|----6---6--|----8-8--8-|
G|---7-7--7--|-8--8-8--8-|-----------|-----------|
D|-----------|-----------|-----------|-----------|
A|-----------|-----------|-----------|-----------|
E|-----------|-----------|-----------|-----------|

(Gm)        (Eb)        (Bb)        (Bb/A)

E|-----------|-----------|-----------|-----------|
B|-8---------|-----------|-8---------|-----------|
G|---7-7--7--|-8--8-8--8-|-----------|-----------|
D|-----------|-----------|----10-10-8|(8)--------|
A|-----------|-----------|-----------|---10-10-10|
E|-----------|-----------|-----------|-----------|

(Gm)        (Eb)        (Bb)        (Bb/A)

E|-----------|-----------|-----------|-----------|
B|-----------|-----------|-6---6-----|-6-6-------|
G|-7---------|-----------|-----------|-----7-7-7-|
D|---8p7-7-7-|-8-8-8-8-8-|----8---8--|-----------|
A|-----------|-----------|-----------|-----------|
E|-----------|-----------|-----------|-----------|

(Gm)        (Eb)        (Bb)        (Bb/A)

E|-----------|-----------|-----------|-----------|
B|-----------|-----------|----------6|-----------|
G|-7---------|-----------|-7---------|-----------|
D|---8p7-7-7-|-8-8-8-8-8-|-------5\3-|-----------|
A|-----------|-----------|-----------|-----------|
E|-----------|-----------|-----------|-----------| etc.

I have figured out the other electronic counter-melody as well but I believe it sounds 
absolutely terrible on guitar and is not appropriate for this website. In saying this, 
however, if you want me to put up that melody then contact me.

I would like to also mention that Crystal Castles are awesome and they were amazing live
at Big Day Out Sydney 2011!
Thank you, feel free to comment or rate this tablature, even by email.

Michael Sacco
Sydney, Australia.