I'll try to explain this stuff.

First, the executive summary: it appears to me that you have a Java applet (Java code downloaded from a web page) that had an error down in the Win32 library. When Java says there was an error in "Native Code", they mean binary Intel x86 code, as opposed to the Java "virtual machine" opcodes.

I went tromping through the Sun Java bug database and found what looks very similar to your issue. Sun has deferred the issue because they couldn't reliably reproduce it.

http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4816519

Was this the result of an attack? I don't know. The existance of long-standing similar bugs in the Sun JavaVM makes me say "no", but that's not something I can say with complete assurance one way or the other. It would appear from Sun's bug database that they have had issues in calling native code from their Java VM that result in errors like this for several years, so I'd attribute this to a bug before I'd lean on an attack.