为什么Tomcat 5.5（使用Java 1.4，在Windows XP 32位上运行）突然挂起？

I've been running Tomcat 5.5 with Java 1.4 for a while now with a huge webapp. Most of the time it runs fine, but sometimes it will just hang, with no exception generated, and no apparant way of getting it to run again other than re-starting Tomcat. The tomcat instance is allowed a gigabyte of memory on the heap, but rarely exceeds 300 MB. Has anyone else run into this issue, and is there a solution for it?I've been running Tomcat 5.5 with Java 1.4 for