This is really irritating. I use Visual Studio 2008 and OpenOffice 2.2.0 Writer at the same time at work. When Visual Studio shows certain modal dialogs, such as a wizard for a new project, or dialogs of the SourceSafe plugin, OpenOffice freezes up completely. It won't even redraw itself, let alone respond to mouse clicks.
Update: I thought Visual Studio was unaffected by this quirk until I started OpenOffice.org Writer at the same time as a SourceSafe "differences" dialog was already open. A message box appeared saying "Unable to complete operation" and then Visual Studio crashed (disappeared instantly). Hmm.