I don't have f-secure, but I did find this on their website:
6. With Android 2.2, I am unable to uninstall. When starting the uninstallation from Manage application, I am prompted ‘Uninstall not successul’. What can I do?
The F-Secure Mobile Security or the Anti-Theft client application uninstallation does not work through application manager uninstallation. This is an operating system feature, which is related to the usage of certain system functionalities. To uninstall F-Secure Mobile Security from Android 2.2 devices, you need to uncheck Device administrators selection from Settings > Location & Security > Select device administrators.
Maybe it will help you out.