Scheduled task interval calculated from stop to start instead of start to start

When running jboss 4.0.2 final with jdk 1.5.0_04 the calculation of the next start of a scheduled operation becomes (time at END of scheduled operation + interval) instead of (time at START of scheduled operation + interval). This causes scheduled operations to shift in time based on the duration of the scheduled operation. This does NOT happen using jdk 1.4 which might hint at the built-in jmx (and timer instance) in the jvm of 1.5 causing the problem?