Can you have 2 sybtypes?

[Starbuck_II]

I was wondering would a barbarian with Frozen Berserker (gives Cold subtype)and Blazing Berserker (gives Fire subtype) have both subtypes?

If so, while in rage you'd be immune to fire and cold damage, yes?

[Fax Celestis]

Yes and yes.

[Kyace]

Ironically, if fire damage did get past his immunity, he'd be vulnerable to it still. The Searing Spell feat from Sandstorm comes to mind.

[Chronos]

In general, there's no problem with having multiple subtypes: A lantern archon, for instance, has four right out of the box. You might want to houserule against some specific combinations (such as Fire and Cold), but the rules don't actually say anything about it.