I exactly had the same behavour and after playing around with fonts and font-extensions I ended up with building my own jasperreports-jar for digging purposes: I discovered that the errormessage was completely misleading and that the root cause originated from java.awt.Front not beeing able to write the Java-temp-directory (java.io.tmpdir). In my case this was the temp-directory of the tomcat-installation. After having changed the permissions of the tomcat-temp-directory everything ran like expected.
