I bought one of these

iPhone 1/8 inch microphone and headphone adapter - 3.5mm 4 conductor TRRS Male to 3.5mm TRS Jacks

Tried it both with my Blackberry 9640 and my wifes Iphone 4, and neither works. The audio works fine, but the mic doesn't, I can head people but people can't hear me.

Can it be some sort of a voltage problem? Could blackberry/iphone mic line not carry enough juice to power up external PC mic?

The adapter you show is just that an adapter. The Iphone mic impedance requirement is 800 ohms and the blackberry mic impedance is 2.2k. Both require different mic types. I would suggest the adapter is doing its job but the devices are mismatched.
do you know the impedance of the mic your using?

Good information - no idea on the mic impendance. Its just a regular, cheap mic that I use for skype on the PC.

I dont think the mic your using is compatable with either. your stuck with two diffferent requirements and I would look for mic's that will work specifically for the device intended.