Category Permalinks

Hello,
I used the fix for category permalinks found here:
http://ww.wp.xz.cn/support/topic/54340
and that fixed post permalinks without a problem. I had changed category permalinks to /tags and that worked fine… but then I tried to change it to /tag and going to a category page gave 404! Also, if I blank out the box to reset to the default /category I get a 404 now!