I'm on an 1810tz with ubuntu 10.04 64bit and Skype 2.2.025-1lucid1 and Skype is working fine.

I solved my mic problems with:

I think the main problem was that my internal mono mic is recognised as a stereo mic and the default setting cancel the signal out.

I installed pavucontrol with Synaptic and started it in a terminal.
In output devices I set the front left to 90% and the front right to 10%. (This way the mic doesn't cancel the signal out) You have to play with the buttons to be allowed to change both value independently.

(I'm pretty sure I found this solution somewhere on the net, but at the moment I don't remember where ... )