As of this writing, the latest version is 1.6.2 and Dahdi version 2.2.0, and there's a standing bug for all cards using the driver: wctdm24xxp.
The cards using that driver are:
Digium TDM2400P/AEX2400: up to 24 analog ports
Digium TDM800P/AEX800: up to 8 analog ports
Digium TDM410P/AEX410: up to 4 analog ports
You will be unable to make outgoing phone calls, until someone rings the line from outside, or if you remove the phone cable and plug it in again.
If you attempt to make an outgoing call, you'll receive an audio message from Asterisk saying: "All circuits are busy now"
If you have compiled your own Asterisk 1.6, then you could apply the patches by the people in the link above.
Use jkroon's patch for Asterisk version 1.6.0.x, and tzafrir's patch for Asterisk 1.6.1.x or 1.6.2.x. You'll need to apply these patches to the source code, then recompile.
I will not be patching my Asterisk as I have no desire to compile Asterisk, to avoid going to fix other things (like Dahdi) in case it broke. So it's Asterisk 1.4 for me, for now.
* Dahdi is the replacement of Zaptel/Zapata. These are the telephony cards' drivers.