strange:
- take a look at the "jasperreports.properties" file(s), find the "net.sf.jasperreports.export.pdf.fontdir.linuxfonts=" line and check whether the folder pointed there actually is correct/have the font file.
There might be multiple instances of that file though.
- you have the 5.0.3 GA version (build #818421). I strongly reccomend to have the 5.0.3 hotfix2 (build #977932). Or upgrade to 5.7...