map.centerAndZoom() has to be before adding any markers?

I didn't see that in the docs, but I've noticed that when I create a
map and start adding markers BEFORE a call to map.centerAndZoom() I get
corrupted/junk maps. (I'm using IE, so not sure if that's yet another
IE-ism, but regardless it makes the app unusable).

In my code I don't know up front where I want the map centered -- is it
ok to center initially on some (?) point, add some markers, and change
the center point again, before adding the rest of the markers? Would
save me having to pre-scan through all the records to find an
appropriate center point then re-process the list generating all the
markers...

TIA,
Chris Bartram