Calls from Skype to Asterisk(SIP), and DTMF codes

I have a problem with dialing extensions when calling from Skype to the number configured on Asterisk.
Asterisk seems to ignore DTMF codes sent by Skype.
Is there any way to configure Asterisk to allow dialing extensions when calling from Skype?

I just got my TDM11B board and have asterisk running with the “demo” dialplan, and I noticed a similar problem when testing by calling with Skype. What’s interesting is that when I dial extentions, the first digit is ignored, but subsequent digits seem to be recognized. So, for example, if I try to dial the “1234” extension as is, I get the message “invalid extension”, and then asterisk hangs up. But if I dial some digit first, followed by “1234”, then I get the extension phone to ring as desired.

When I call the asterisk machine with a cell phone, however, I don’t have this problem. On the other hand, I haven’t had much trouble calling other PBX’s with Skype. Might it be a bug that’s unique to Skype-calling-asterisk?