How many languages do you have installed/configured?

Have you applied the relevant bug fixes to your site? See: Known Bugs (and fixes) with v1.5.4

Does the same problem happen with a fresh install in a new database (ie: with test data)? By using the demo database it may help rule out whether the problem is related to something unique to the server or to any plugins installed.

Quote Originally Posted by drgr33n View Post
No plugins installed that would effect the category system.
Please list them anyway.