Are there resource constraints? You haven't given much information to diagnose the problem.
1) What specific OS distribution?
2) What JDK/JRE for JBoss?
3) What processor, speed and memory?
4) What configuration instance of JBoss (including servlet container)?
5) What compiler for Jasper?
6) What is the RSS and shared memory for the runtime instance?
7) What specific JAVA_OPTS?
This will help the folks offer comments or suggestions.
Sorry, my fault
1) RedHat quite old > 2 years
2) JDK 1.3.1_07-b02
3) 512MB 800MHz
4-7) out of the box JBoss-3.2.1 default
I tried it on a new Suse as well - same problem.
So I thought it must be common enought for people to know about.