Cannot create multiple temporary XMPP accounts in the same session

TM version: 0.5.0b1 (based on Instantbird 1.6a1pre)

Steps to reproduce:

• Create a temporary XMPP account -> succeeded
• Create another temporary XMPP account. The Accounts window shows Error: without any details (please see the screenshot).

Debug Log shows:

LOG (@ prpl-jabber: XMPPParser.prototype._logReceivedData re[//modules/xmpp-xml.jsm:349)](//modules/xmpp-xml.jsm:349))
received:
<iq xmlns="jabber:client" id="396b4d85-c241-7747-ad55-e1025d6a2ce9" type="error" from="jabber.otr.im">
<error xmlns="jabber:client" type="wait">
<not-acceptable xmlns="urn:ietf:params:xml:ns:xmpp-stanzas"/>
</error>
</iq>