Adium 1.2.6 sent ASCII control characters in the <version> string of an XMPP message, which caused an XML parser error that caused XML processing to stop which eventually resulted in a ping timeout. (I'm fairly certain this is the explanation for the reconnects people were experiencing.)
1.2.7b1 fixed the version string that 1.2.6 was sending, which would alleviate the reconnects if everyone in your contact list upgraded from 1.2.6 (a downgrade would have worked as well). If anyone in your contact list was still running 1.2.6, however, the invalid version string would be sent, the XML parser would fail, and you would eventually get the ping timeout which would cause a reconnect. As such, the fix would only work if there were no 1.2.6 clients in your contact list that could respond to the jabber:iq:version request.
The real issue seems to be that the XML parser will not process XMPP messages after an invalid XML character is encountered. This is effectively similar to a ticket I posted to Pidgin:
http://developer.pidgin.im/ticket/6031
This could be the reason for:
http://trac.adiumx.com/ticket/10347
Perhaps the user had an Adium 1.2.6 client in their contact list, which caused the ping timeouts. This is speculation, but this issue could cause what the user was seeing.
It also can explain what other users were experiencing under that ticket (10347). In this case, not receiving XMPP messages and the disconnection issues are related.
I have posted this in some of the comments of the bug reports I have referenced, but I felt like it deserved a new ticket as the original issue (http://trac.adiumx.com/ticket/10324) still exists: connections will cycle if invalid XML characters are sent, presumably because XML parsing ceases.