asdoc.bat on Windows 7 (64) "cannot find main class flex2.tools.ASDoc"

Although I can run asdoc in FlashBuilder (via ant), I'd like to use it
directly from the command line.
I understood that asdoc.exe is no more supported because of 32/64 bit
issues, and asdoc.bat and aasdoc.bat now should be used instead.

But calling asdoc.bat (simply as "asdoc.bat -help" or with a complete
set of parameters as shown in Adobe's examples)
from a command line (with or w\o admin rights) on my Windows 7 64 bit
system
results in that error:
"main class flex2.tools.ASDoc" could not be found.

What am I missing?
Anything wrong with my Java or Flex installation? Any PATH variable missing?

asdoc.bat at the end is just one single line of "code":
java -Xmx1024m -Dsun.io.useCanonCaches=false
-Xbootclasspath/p:"%FLEX_HOME%\lib\xalan.jar" -classpath
"%FLEX_HOME%\lib\asdoc.jar" flex2.tools.ASDoc
+flexlib="%FLEX_HOME%\frameworks" %*

Thanks!
Hans