I was previously using jQuery 1.3.2 with UI 1.7.1 and when doing so and using the "position:center" option the dialog was always positioned absolutely.
I have now upgraded to jQuery 1.6.1 with UI 1.8.13 and now the same code is creating a div which is positioned relatively. This has the adverse affect that the dialog is affectively anchored to the bottom of the page, so resizing the window to be smaller can float the dialog off the top of the viewport.
Has any else experienced this? Any ideas?