the "dynamic attach" support was not added until jdk 1.6, so you won't be able to just attach to it. however, if you do the normal jmx remote attachment stuff (e.g. setup a remote connector on a certain port), i would imagine jvisualvm would be able to attach to it (as a "remote" vm).
I vaguely remembered some option that was required, but that was to monitor
a Java 1.4.1 VM with VisualGC ; [url http://java.sun.com/performance/jvmstat/]jvmstat ^[url http://java.sun.com/performance/jvmstat/]jvmstat^
The instrumented HotSpot JVM ships with J2SE 1.4.2 and later, providing always-on instrumentation. The HotSpot JVM, verion 1.4.1, also includes the the instrumentation, but it must be enabled with the -XX:+UsePerfData flag.