I have been using iReport 3.7.5 with jasperserver 3.7.1 without problem since Sep 2010. But now I'm faced with the "unknown hyperlink target 0" also. I figured the difference of what I did so far was the other reports that worked fine were edited using iReport plugin after they were uploaded to jasperserver, while this problematic one is simply uploaded with no further editing. So I tried opening the jasperserver report unit via iReport plugin, made a small edit, and replace the report unit with that file. Then it worked. However, I did remember previously reports uploaded without further edit did work, and only this particular one did not work. Anyway, this may be worth a try if you do not with to downgrade iReport or upgrade jasperserver. Cheers.
