Try a disable/uninstall of the og module, then re-install the module.

Sometimes it helps to restore and/or repair these kinds of problems.

Another option might be that you need to increase the memory size of your Drupal site  (add 25 to 50% of memory, or just double it). And then retry uninstall/reinstall one more time. Because each time you install a module, your site will be using more memory. So at some poi nt (if you never increase the memory), you'll hit your available memory limit.

If that doesn't help, then check your log files (both Drupla logs and/or server logs) to find some kind of indication of possible errors.