Ok. This is stupid.
I went berserk in the dataset, and tryed everything. Open with*.*, Delete some files, run custom tool etc.
And when i tried to go and change a random field name of a random table, then save. It all worked out great. I now have access to my dataset
Hmm.. It still pops up all lined up horisontenally when i open the solution, and when i close and open dataset it looks all messy again. But i can move them at least.
Also this was a great way to auto arrange items in dataset:
"Hi, Maybe its so late for answering this question...
I did the following steps and it works:
1- Under .xsd file in solution explorer, find .xss file and delete it.
2- In solution explorer, right click on your dataset and choose Run Custom Tool."