That's so odd. The only thing I found on OpenOffice's problems site was this: http://www.openoffice.org/issues/show_bug.cgi?id=1246
But that's a pretty old bug (2001, it says), and it says it was fixed. The only way I can think of fixing it is to build OO from source or downloading one of the older releases and seeing if it works.
PS I remembered as I read your post that Gnome won't let you drag windows past the taskbar, sorry