QSYSObjectPathName -- Length is not valid???

Okay, I'm baffled. I have this line of code:

QSYSObjectPathName fileName = new QSYSObjectPathName("%LIBL%",
"BLPEDI94", "MAVERIK", "MBR");

and when I run it in my complex environment it throws this exception:

com.ibm.as400.access.ExtendedIllegalArgumentException: objectName
(/QSYS.LIB/%LIBL%.LIB/BLPEDI94.FILE/MAVERIK.MBR): Length is not valid.

If I copy and paste the line of code into a simple program which just
does that and then prints the result, I get the result printed. But in
my multi-threaded message-processing system, I get the exception. Not
only that, the line of code is working correctly in the production
environment and it's just failing in the test environment.

In all cases it's the QSYSObjectPathName class which is being loaded
from here:

/QIBM/ProdData/OS400/jt400/lib/jt400Native.jar

I'm running V6R1 on this test machine and Java version 1.5.

I don't see anything in Google about this except some unrelated things
about data queues which have the wrong length, and I downloaded the
JTOpen source code (version 6.6) and I don't see this error message
being thrown from that constructor, or anywhere in the class. Anybody
have any idea what this is all about?

Regards
Paul Clapham