@Michael H: I already mentioned that its caused by the theme i use. Why is there never before mentioned that you should have a 2.3 ready theme before uploading?
Because if your theme had been written correctly in the first place and didn't use direct database calls, then it would work fine.
There's always a way to write things that will be incompatible. Themes, plugins, anything external to WordPress can break with *any* upgrade. There's no way to know what themes will break, because there's tens of thousands of them.
But for future compatibility, here's a tip. If you see a theme that contains SQL code, then it's quite likely to break at some future point. Avoid using it. Plugins often use SQL code, but if they're using that code to access normal wordpress tables (instead of their own tables), then they're at risk too.