When I join a particular channel on an IRC server at work, Piding 2.5.1 crashes if the encryption plugin is enabled (no crash if pidgin-encryption is disabled). Please see the attached pidgin.rpt for details.
When joining other channels on the same server, Pidgin survives. Also, there was no crash when I joined that channel with Pidgin 2.4.2.
Here's a chat excerpt from #pidgin:
(14:11:58) SimGuy: unfortunately I don't know exactly how that plugin works, but it seems that it's doing something wrong with a hash table on joining that channel
Unfortunately the IRC server at work is firewalled, but please let me know if there are other ways I can help debugging this issue.