Environment variable resolution bug

There seems to be some sort of bug in the way environment vars get resolved.
Maybe something to do with both level of depth and alphabetical sequencing.
I was wondering if there was a fix....
EG:
%DERBY_HOME%=%J2EE_HOME5\javadb
PATH=%DERBY_HOME%\bin;
In path %DERBY_HOME% stays unresolved so when I try and execute commands in
the %DERBY_HOME%\bin directory, it doesn't find them.
path still says %DERBY_HOME%\bin instead of C:\Sun\SDK\javadb\bin
%DERBY_HOME% resolves correctly on it's own to C:\Sun\sDK\javadb
Any ideas?