Thats ok, its a known issue. You can disable the code checks plugin until that is fixed. As long as its not half of the plugins that don’t work you should be fine.
Just as a side note, one of the commiters from Lucene (Apache Project) does not recommend anyone to use Java 7 for anything important, since it has some known issues with the JIT Optimizations, which seems to break some loops. It is a known issue, but its scheduled to be fixed in a later update to the platform.
More info here: http://www.lucidimagination.com/blog/2011/07/28/dont-use-java-7-for-anything/
Not sure about jMonkey’s position regarding Java 7, but for me, an “optimization” that can break loops seems a big enough reason to not support it until its fixed.
Hope this can clarify some of the problems related to Java 7, and alert new users about possible problems.