I had this happen to my own tiki awhile back. The issue was not enough memory, my php.ini was set really low, it's a wonder anything worked.
As Rick said, check to make sure your ok with the Tiki Server Check, if you have any issues accessing your hosting configurations, your hosting company will do if for you.
Hope you get it squared away!
If you do, please report back on what the issue was, and the solution.