Kossel Mini Problem

Ok, so this apst week I decided that I would start building a Kossel Mini printer. I printed out all the parts on my Prusa Mendel and order the Open Beam and various nuts & bolts. Yesterday I started assembling the frame. I got it all together and it looks good except that when I lay it on its side, there is a considerable amount of wobble (~3 mm) diagonally (as in corner to corner - like a desk with legs that aren't the same length). Something is not square and Im not sure why.

Could it be because of my printed vertices? I ran into some warpage problems when printing them. The warping is on the "legs" of the parts so I thought it wouldnt affect the uprights, but maybe it does?

Has anyone else run into this problem before?

Any help would be appreciated.

Thanks,
-Lucas