Known bugs in version 1.0.1
When Twinkle receives an ICMP message as response on an outgoing request, it should abort the current SIP transaction and possibly retry an alternative destination if a DNS lookup resulted in multiple destination.
Unfortunately the processing of ICMP messages does not always work. The ICMP messages may queue up forever on the socket receive queue.
As a temorary fix you can apply this patch and recompile Twinkle.