plot plugin crashes firefox with multiple plot groups under XP

to reproduce

Windows XP SP3, JDK6 (fails under u6 and U10 - others untested) install hudson
(1.259) and run using embedded winstone.

install plot plugin.

create a freestyle project with no source code management or build triggers.

Build using the following "Execute Windows batch command"

ECHO YVALUE=%BUILD_NUMBER% > build.property
ECHO YVALUE=0 > zero.property

Add "post build action" of "plot build data" configured with two plots each
with 2 series as follows

plot group=group1
plot title=plot1
Data series file=build.property
Data series legend label=build number
Data series file=zero.property
Data series legend label=zero

plot group=group1
plot title=plot2
Data series file=build.property
Data series legend label=build number
Data series file=zero.property
Data series legend label=zero

save and build twice to create some data.

In firefox view the project and pick on the "Plots" link. All OK.

Now to bust it:

make sure java console is running

reconfigure the project and change the plot group of the second plot
to "group2"

save and click the "Plot" link again.

Then Firefox appears to lock up, and the java console shows attached exception.
any subsequest link clicking in the browser causes and application error
acessing invalid memory (different details some times but often

The instruction at "0x00000000" referenced memory at "0x00000000". The memory
could not be "read".

restart FF and reconfigure the project back to just have one plot group and all
is OK again.

Does not cause any problems with IE.