Redmine

Hello All,
I have installed redmine on Ubuntu 10.4LTS. The following are the version details
Redmine-1.4.2
Ruby-1.8.7
Rails-2.3.14.
I have installed mongrel.
I have placed the plugins importer and spent time in /vendors/plugins/.
I have followed the installation process defined in readme .doc for importer and spent time plugins respectively. I did not get any error when installing them. I have restarted the redmine.
When I clicked on to Administration link and then Plugins, I am not able to view the plugins I have installed. It displays as No Data to Display. I have checked again for permissions for the folders and availability of the code on to the /vendors/plugins . All are set as per to the instructions.
Any clues why is it the plugins are not visible in the plugin list.

Thanks,
SR