damaged headphone socket?

Hi,
I have a very horrible feeling that i've somehow managed to break the headphone socket on my imac G5, but I'm hoping one of you experts tell me I haven't.....

I've had it connected to an external amp and speakers via the headphone socket for a while but recently I've been switching the jack between the imac and my ibook. But now when I put the jack back into the imac it won't go all the way in - sound from the imac cuts out but doesn't come through the external. I've also tried connecting normal headphones and it's the same so it's definitely a problem with the socket....

Any idea what could have happened? When i've been switching between imac and ibook there's been that feedback sound from the amp just as it goes in but that's just a sound, right? I can't imagine that would do any damage.....

Thanks

bump (sorry)

Are you sure there's nothing stuck in the hole?

Yup, nothing in there. I just don't get it... Problem is too that it's not even my imac - I'm looking after it while they're away....

Anyone wanna take a stab at how much it's gonna cost to repair? If I'm lucky then it might still be under warranty - have the g5 imacs even been out for a year yet?