irb(main):013:0> jira.getIssue("CONF-3459")
RuntimeError: org.apache.xmlrpc.XmlRpcException: Invalid character data corresponding to XML entity ř
from ./jira4r.rb:39:in `method_missing'
from (irb):13

This is the same error as CONF-1188 – you can fix it by upgrading your XML-RPC dependency to 1.2-b2-conf1188 (in the Atlassian repository), or if you're feeling brave, to 2.0.

Setting as critical because it makes most of the XML-RPC API useless as soon as one of your issues contains a high-bit char.