Off the top of my head-
I think we've agreed that tabbed docks take longer to load than regular docks, so if you've added a tabbed dock you would see a slowdown right away.
I've seen several posts lately about the weather docklet being problematic right now, so if you're running that it might be bogging down your start up, don't know.
Some other docklet might be causing a problem, you might try checking the "disable docklets" option under Object Dock's configuration / troubleshooting section to see if that speeds you up.
Might be fighting for system layering resources if you have any widgets or DTX objects loaded in the same screen area as a dock. I do load up DTX objects and widgets all the time long with Object Dock, but they don't occupy the same screen space. Don't know, might cause a problem under the right circumstances.
Also might be fighting for layering resources if you're loading up Object Dock while dvd player software or ATI's tv player are already running.