If you group the frames you can move them around without changing their relative positions. However, you'll need to (temporarily) un-group them to make any changes.
P.S. Looking a bit into the future, 1.5.0svn looks like it'll do relative frame positioning - among lots of other good stuff - so it's worth keeping an eye on how that's going (or even compiling it yourself if you want it now).
in 1.4.x you'll need to ungroup the items to change their relative position.
but if you just want to edit their content, you can alt-click them to select a single item inside of a group... or even alt-double-click to enter its edit modus.
a well hidden feature, but an existing one :-)
(and iirc the alt-click "trick" also works for selecting the table's cells)
p.s.: concerning scribus 1.5svn: the easiest solution to try it out (or even using it) "under windows" is to setup a virtual machine with a recent ubuntu in it and add the PPA created daily by the ubuntu project (on request by mr. shuttelworth himself...)
it's not hard to do and it's all klickibunti, but you should look for somebody in your neighborhood to help you set up the virtual machine.