If you haven't already, download Eyeball from the Eyeball package page. This jar file is self-contained (it includes all the Jena jars it needs so that it can run standalone).
Pick one of your RDF files; we'll call it FOO for now. Run the command-line command:
java -jar eyeball-2.4.0-exec.jar -check FOO
You will likely get a whole bunch of messages about your RDF. The messages are supposed to be self-explanatory, so you may be able to go ahead and fix some problems straight away.
(You may also want to try the experimental Eyeball GUI, but you'll still need to start it from the command line.)
If the messages aren't self-explanatory, or you want more details, you'll want to move on to the brief guide.