I released a new version of the symfony plugin to address this issue:
http://code.google.com/p/firesymfony/issues/detail?id=9
The problem was that the new version of symfony has moved the method:
sfWebDebugPanelConfig::removeObjects()
to:
sfDebug::removeObjects()
Please send me feedback on this issue,
link to release: http://www.symfony-project.org/plugins/firesymfonyPlugin/1_0_8
Regards,
Alvaro