unable to build rev 6494+ under Windows XP

[Alex Mitchell <lexaay at gmail dot com>]

I just grabbed the latest source from svn, and was unable to build
under windows. rev 6493 is ok, but rev 6494 onwards gives me the
following error:

C:\Documents and Settings\alex\My Documents\projects\kawa>ant
Buildfile: build.xml

build-tools:
    [mkdir] Created dir: C:\Documents and Settings\alex\My
Documents\projects\kawa\tools
    [javac] Compiling 5 source files to C:\Documents and
Settings\alex\My Documents\projects\kawa\tools
    [javac] Note: Some input files use unchecked or unsafe operations.
    [javac] Note: Recompile with -Xlint:unchecked for details.

build-settings:
     [echo]
     [echo]         version=1.9.90
     [echo]         dist.kawa.jar=C:\Documents and Settings\alex\My
Documents\projects\kawa/kawa-1.9.90.jar
     [echo]         build.dir=C:\Documents and Settings\alex\My
Documents\projects\kawa
     [echo]         with-awt=true
     [echo]         with-swing=true
     [echo]         with-sax2=true
     [echo]         enable-jemacs=false
     [echo]         enable-xml=true
     [echo]         enable-servlet=false
     [echo]

preprocess:
    [xcopy] Copying 1 file to C:\Documents and Settings\alex\My
Documents\projects\kawa\kawa

java-classes:
    [javac] Warning: kawa\Version.java modified in the future.
    [javac] Compiling 554 source files to C:\Documents and
Settings\alex\My Documents\projects\kawa
    [javac] C:\Documents and Settings\alex\My
Documents\projects\kawa\gnu\expr\KawaScriptEngine.java:141: cannot
find symbol
    [javac] symbol  : method
evalToResultvalue(gnu.mapping.Environment,gnu.mapping.CallContext)
    [javac] location: class gnu.expr.CompiledModule
    [javac]         return
cmodule.evalToResultvalue(engine.factory.getEnvironment(context),
    [javac]                       ^
    [javac] Note: Some input files use or override a deprecated API.
    [javac] Note: Recompile with -Xlint:deprecation for details.
    [javac] Note: Some input files use unchecked or unsafe operations.
    [javac] Note: Recompile with -Xlint:unchecked for details.
    [javac] 1 error

BUILD FAILED
C:\Documents and Settings\alex\My
Documents\projects\kawa\build.xml:350: Compile failed; see the
compiler error output for details.

Total time: 3 seconds

This is using java 1.6.0_17-b04, under Windows XP SP3.

I haven't had any problems with the latest source under MacOS or
Ubuntu. Any ideas what could be wrong?

thanks,
Alex