Internal Server Error when Managing Tags

When I go to the Tags page to try and create some tags (edit-tags.php) I get a non-specific Internal Server Error. I compared the page to one from another WP site I have running and there are no differences except it works on the other site. Why would this be happening? The only difference in the architecture of the 2 sites is that the one that’s working has WP in the root and the one that’s not has WP in a subdirectory (which is to say it’s in a folder in the root – it’s not buried way far down). Any help would be greatly appreciated. Thanks a lot.