I get the following error on Aurora / Earlybird 14.0a2 (2012-04-25) with
Enigmail 1.5a1pre nightly (2012-04-22) when trying to decrypt a message:

Timestamp: 25-4-2012 17:25:20
Error: enigmailMessengerOverlay.js: messageDecryptCb: caught exception:
TypeError
Message: 'Cc[NS_IPCBUFFER_CONTRACTID] is undefined'
File:
file:///C:/Users/OEEkker.AMC/AppData/Roaming/Thunderbird/Profiles/k4l90cvh.default/extensions/%7B847b3a00-7ab1-11d4-8f02-006008948af5%7D/components/enigmail.js
Line:    2307
Stack:
@file:///C:/Users/OEEkker.AMC/AppData/Roaming/Thunderbird/Profiles/k4l90cvh.default/extensions/%7B847b3a00-7ab1-11d4-8f02-006008948af5%7D/components/enigmail.js:2307
@chrome://enigmail/content/enigmailMessengerOverlay.js:909
@chrome://enigmail/content/enigmailMessengerOverlay.js:832
@chrome://enigmail/content/enigmailMessengerOverlay.js:743
@chrome://enigmail/content/enigmailMessengerOverlay.js:504
@resource://enigmail/enigmailCommon.jsm:1214