I'm unsure of what version of tiki are you using, however initlib.php contains tempdir which returns a temp folder too.
I remember I had a similar problem on my first tiki installation at a host. I created a local tmp in my webspace and configured in the way way.
Probably worth while empty the cache folders incase you have anything in there causing the glitch.
the data comes from user modules, if this a fresh install, or a upgrade?