Dialog in 1.8 IE8 WInXP modal dialog causes scroll of main window

Dialog in 1.8 IE8 WInXP modal dialog causes scroll of main window

Hi
I was running an aplication with 1.7.2 containing dialogs, but decided to add the new autocomplete plugin and upgraded to v1.8.
Everything is fine in Firefox and Chrome, but I have found that in IE8 on winXP platform the dialog scolls the page upwards off the screen and then opens the dialog box also above the top of the screen.

I am aware of the beforeClose change, have I missed something else that needs changing with the dialog?

Thanks