hook_uninstall not working
Are the functions you are calling from your implementation of hook_uninstall() defined in your .module file? If that is the case, those functions will not be found, as the module file is not anymore loaded in memory.


  When hook_uninstall() is called, your module will already be disabled, so its .module file will not be automatically included. If you need to call API functions from your .module file in this hook, use drupal_load() to make them available. (Keep this usage to a minimum, though, especially when calling API functions that invoke hooks, or API functions from modules listed as dependencies, since these may not be available or work as expected when the module is disabled.)