There are no speed differences between 6.6 and 6.7. You may have other things going on.
First - clear DRC markers (Tools>Reset Error Markers).
Next - AD analyzes ground and power nets every time you move a component. If your board is fairly large, this can take some time. You can "hide" a net so it doesn't get analyzed by going to View>Connections>Hide Net, and clicking on any ground or power pin.
Finally - the speed of operations on the PCB is very closely related to how many online design rule checks (DRC) need to be done. If you have a lot of design rules, you may want to turn off the online checks. You can then do periodic batch checks. To turn off online checks, go to Tools>Design Rule Check, click on "Rules to Check" and right click anywhere in the table on the right side of the dialog. You will see the options to turn off or on the design rule checks under certain circumstances.
If the above don't speed up the operations, then you need to look at what else your computer may be doing to cause the delay. Hit CTRL-ALT-DEL to bring up the system Task Manager, go to the "Processes" tab, and look to see if it is really AD (DXP.EXE) that is using the CPU time.