native2ascii and JDK/JRE

[Trying again with a better subject and no garbage at the end...sorry.]

Excuse me if this has been answered or documented elsewhere, I've been searching 
for the past couple of hours and have found very little on this issue.

I have a project that uses the native2ascii task, that works fine on a machine 
with JRE 6 (1.6.0_65-b14-462-11M4609).

However, when trying to run the same project under JRE 7 (1.7.0_67-b01), it 
fails with the Java message "Error starting Sun's native2ascii."

Eventually I was able to fix this issue by copying tools.jar from a JDK into the 
lib file of my JRE.

I'm surprised to have to go to such lengths to fix this issue. I'm also 
surprised there's not more documentation in the native2ascii task in the Ant 
manual pointing out this problem.

Is there a more elegant solution out there than copying tools.jar? (I'm using 
Apache Ant under the DITA Open Toolkit; most DITA OT users just use the JRE.)

Thanks for any help or suggestions,
Simon

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Simon F. Bate
Senior Technical Consultant, Scriptorium Publishing Services, Inc.
[email protected] <mailto:[email protected]>
phone: 919.433.2606
twitter: @simonbate