It may be related to the ssl certificate being self signed. Try importing the certificate into the java jre keystore.
After downloading the certificate it's something like:
/usr/lib/jvm/java-6-openjdk/jre/bin/keytool -keystore /usr/lib/jvm/java-6-openjdk/jre/lib/security/cacerts -import -file dotq.dotquality.de -alias dotquality
