Area contents overflows area - with use.extensions=1

When I turn on extensions (and I have places saxon651.jar in my
classpath, and am using saxon.jar v652), When it gets to a certain page
(can't tell where, but fairly early on), the XSLT process just hangs and
makes no further programs but keeps printing out "[INFO] area contents
overflows area". The file size no longer grows, and I have to kill the
process. Any suggestions?

At present, I'm not actually using any calls to any extensions. Its my
normal doc that I've run a million times. I just turned extensions on
and it no longer works.

Brian