USAP,
So you stick the jack halfway in and then wriggle it to get the on-board speakers to work? If so, then, clearly, the on-board speakers think something is still plugged in even though there isn't. Can you repeat this problem?
Mine have been fine from day one and I'm constantly switching back and forth
Enk1du,
This is the first instance of something being physically wrong with the audio, so let's see if we can get to the bottom of it before sweating it. Second, PCMCIA won't be a solution cause it doesn't have one.

I can tell you that with a good set of headphones, this thing puts out amazing audio. For even more amazing audio I'm running a firewire audio interface through a mixer to some monitoring speakers and will be switching to an ExpressCard solution as soon as somebody puts one out.......come on ECHO or M-Audio.