E_NOTICE errors from boost.module

We are getting a lot of notice errors from boost module. The most common errors are (other errors show up if the requested node does not exist):

Notice: Undefined variable: filename in _boost_ob_handler() (line 1404 of /home/xx/public_html/sites/all/modules/boost/boost.module).

Notice: Undefined index: _boost_relationships in boost_cache_set() (line 2287 of /home/xx/public_html/sites/all/modules/boost/boost.module).

Notice: Use of undefined constant headers_list - assumed 'headers_list' in boost_headers_contain() (line 1470 of/home/xx/public_html/sites/all/modules/boost/boost.module).

The Status Screen reports that the module was installed correctly.
We are running Pressflow distribution 6.20.

Thanks