JSP/Tomcat 6 "org.apache.jasper.JasperException: java.lang.ArrayIndexOutOfBoundsException"

We noticed "org.apache.jasper.JasperException: java.lang.ArrayIndexOutOfBoundsException" on our JSP pages in the morning. I have copied the entire exception stack trace below for reference.

My first guess was the jsp pages have some issue where we are trying to access some index which has not been assigned. But we realized it's the server which ran our of space. so the first exception was "

java.io.IOException: There is not enough space in the file system.".

Why tomcat has to throw such an non intuitive error message? Why?  Not sure if it's tomcat's fault or the underneath framework is messing up.

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org.apache.jasper.JasperException: java.lang.ArrayIndexOutOfBoundsException
 org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:522)
 org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:416)
 org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
 org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
 sun.reflect.GeneratedMethodAccessor209.invoke(Unknown Source)
 sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
 java.lang.reflect.Method.invoke(Method.java:600)
 org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:269)
 java.security.AccessController.doPrivileged(AccessController.java:284)
 javax.security.auth.Subject.doAsPrivileged(Subject.java:727)
 org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:301)
 org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:162)

root cause
java.lang.ArrayIndexOutOfBoundsException
 java.io.OutputStreamWriter.write(OutputStreamWriter.java:250)
 java.io.Writer.write(Writer.java:152)
 org.apache.log4j.helpers.CountingQuietWriter.write(CountingQuietWriter.java:44)
 org.apache.log4j.WriterAppender.subAppend(WriterAppender.java:308)
 org.apache.log4j.RollingFileAppender.subAppend(RollingFileAppender.java:236)
 org.apache.log4j.WriterAppender.append(WriterAppender.java:159)
 org.apache.log4j.AppenderSkeleton.doAppend(AppenderSkeleton.java:230)
 org.apache.log4j.helpers.AppenderAttachableImpl.appendLoopOnAppenders(AppenderAttachableImpl.java:65)
 org.apache.log4j.Category.callAppenders(Category.java:203)
 org.apache.log4j.Category.forcedLog(Category.java:388)
 org.apache.log4j.Category.error(Category.java:319)
 com.jpmc.tao.common.logging.Logger.error(Logger.java:167)
 com.jpmc.tao.presentation.controller.FrontController.process(FrontController.java:61)
 org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
 sun.reflect.GeneratedMethodAccessor225.invoke(Unknown Source)
 sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
 java.lang.reflect.Method.invoke(Method.java:600)
 org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:269)
 java.security.AccessController.doPrivileged(AccessController.java:284)
 javax.security.auth.Subject.doAsPrivileged(Subject.java:727)
 org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:301)
 org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:162)
 java.security.AccessController.doPrivileged(AccessController.java:251)
 java.security.AccessController.doPrivileged(AccessController.java:251)
 org.apache.jasper.runtime.PageContextImpl.doForward(PageContextImpl.java:706)
 org.apache.jasper.runtime.PageContextImpl.access$1000(PageContextImpl.java:71)
 org.apache.jasper.runtime.PageContextImpl$11.run(PageContextImpl.java:664)
 java.security.AccessController.doPrivileged(AccessController.java:251)
 org.apache.jasper.runtime.PageContextImpl.forward(PageContextImpl.java:662)
 org.apache.jsp.default_jsp._jspService(default_jsp.java:54)
 org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
 org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
 org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
 org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
 javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
 sun.reflect.GeneratedMethodAccessor209.invoke(Unknown Source)
 sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
 java.lang.reflect.Method.invoke(Method.java:600)
 org.apache.catalina.security.SecurityUtil$1.run(SecurityUtil.java:269)
 java.security.AccessController.doPrivileged(AccessController.java:284)
 javax.security.auth.Subject.doAsPrivileged(Subject.java:727)
 org.apache.catalina.security.SecurityUtil.execute(SecurityUtil.java:301)
 org.apache.catalina.security.SecurityUtil.doAsPrivilege(SecurityUtil.java:162)
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Any thoughts?
Manisha