I have been having similar problems and when these lines were inserted I got this:
Warning: main(file:///C|/Users/george/AppData/Local/Temp/admin/includes/configure.php) [function.main]: failed to open stream: No such file or directory in /home/mushroom/public_html/catalog/googlecheckout/gcheckout.php on line 34
Fatal error: main() [function.require]: Failed opening required 'file:///C|/Users/george/AppData/Local/Temp/admin/includes/configure.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/mushroom/public_html/catalog/googlecheckout/gcheckout.php on line 34
Any ideas? thanks in advance