Adium update causes instability with jabber servers including UM Chat
Update:Version 1.2.7 was released over the weekend and fixes the underlying cause of this issue.
There is an issue with the 1.2.6 version of the Adium messaging client for OS X and jabber servers such as the one powering UM Chat. The best current solution is to disable your UM Chat account in Adium and recreate it. Others have reported that going back to version 1.2.5 works.
I am looking for a public mirror that still has Adium 1.2.5 available for download. Download Adium 1.2.5(via adiumx.cacheflyu.net).