When raiser doesn't quite go all-in.... 20+2

[proell]

Party Poker No-Limit Hold'em Tourney, Big Blind is t200 (6 handed) converter

Button (t1260)
SB (t1290)
BB (t1301)
UTG (t915)
MP (t1459)
Hero (t1775)

Preflop: Hero is CO with Q[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/diamond.gif[/img].
<font color="#CC3333">UTG raises to t600</font>,
Hero???

I hate this because the raiser left themselves with 300 chips and I'm not sure what to make of it. They're brain dead and don't want to commit all their chips with a mediocre hand, or they want some company for their monster?

Curious what people think UTG has and what you would need to make this call.