chrome extension loads, but does nothing

I'm running

$ lsb_release -ds
Ubuntu 10.04.1 LTS
$ uname -rv
2.6.32-27-generic #49-Ubuntu SMP Thu Dec 2 00:51:09 UTC 2010
$ sudo aptitude update ; sudo aptitude full-upgrade
...
0 packages upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
...
$ firefox --version
Mozilla Firefox 3.6.13, Copyright (c) 1998 - 2010 mozilla.org
$ google-chrome --version
Google Chrome 8.0.552.224

I checked out the chrome ext with

CHREXT_ROOT="${HOME}/bin/zotero/google-chrome"
CHREXT_DIR="20101229"
CHREXT_PATH="${CHREXT_ROOT}/${CHREXT_DIR}"
CHREXT_SOURCE_ROOT="https://www.zotero.org/svn/connector/chrome/trunk"
mkdir -p ${CHREXT_PATH}
pushd ${CHREXT_ROOT}
svn co ${CHREXT_SOURCE_ROOT} ${CHREXT_DIR}
popd
echo -e "load chrome extension from folder='${CHREXT_PATH}'"

The files are there, and permissions look appropriate:

$ ls -al ${CHREXT_PATH}
> -rw-r--r-- 1 me me 6797 2010-12-29 22:55 global_common.js
> -rw-r--r-- 1 me me 2609 2010-12-29 22:55 global.html
> drwxr-xr-x 3 me me 4096 2010-12-29 22:55 images
> -rw-r--r-- 1 me me 2414 2010-12-29 22:55 inject.js
> -rw-r--r-- 1 me me  487 2010-12-29 22:55 itemSelector.css
> -rw-r--r-- 1 me me 1752 2010-12-29 22:55 itemSelector.html
> -rw-r--r-- 1 me me 2477 2010-12-29 22:55 itemSelector.js
> -rw-r--r-- 1 me me  445 2010-12-29 22:55 manifest.json
> drwxr-xr-x 6 me me 4096 2010-12-29 22:55 .svn

I can load the extension in chrome by

0 browse to chrome://extensions/
1 expand the "Developer mode" twistie
2 click button="Load unpacked extension..."
3 enter folder=valueof(${CHREXT_PATH}) in the resulting file dialog, hit OK

When I do that, "Zotero Connector for Chrome" shows @ top of list=Extensions, with no obvious errors, and looking like google says it should.

However

- after loading the extension, no additional icon appears next to the chrome address bar

- when I browse to a journal article, no additional icon appears next to the chrome address bar

By contrast, if I start firefox and browse to that same article, I get the zotero page icon in the firefox address bar.

What must I do to make the chrome extension behave appropriately?

Your assistance is appreciated, Tom Roche