I've recently installed "Timesheets" but it gave me some troubles with the task visualisation so I decided to not use it. But when I try to delete it or uninstall it I'm not able to do it.
Here is an screenshot so you can see that the uninstall button is not available (gray). When I click not it nothing happens.

I don't want to wait for the free trial expires, that's a month from now.
Can anybody help me with this ?