SL360 really slow - objects with states

I was wondering if anyone has come across this issue recently with SL360.

I have a rectangle with 2 states on it - normal and hover.  The rectangle has an image for its background and then another rectangle with text in it layered on top, in both states.  What I am finding is the slide (or the objects) are becoming really slow to move, edit, etc.  

For example, I copy one of the boxes and then move it, but after I move it SL becomes unresponsive for a good 5-10 seconds.  If I then go and edit the states it takes another 5-10 seconds for it to go into edit mode, and then anything I do in there also takes a considerable amount of time to action.  So if I go and change the background image it can take me anywhere between 20 and 60 seconds to actually make the change and apply it because it is running so slow.

I found this on another project where a text box had multiple states.  It was painfully slow to edit the states, even just clicking onto a state took 5-10 seconds, and then an additional 5-10 seconds to get the cursor in the text box once I clicked on it, and then a further 5-10 seconds to apply that change.  There was nothing fancy in this one, just about 7 states, all with just text in them.

It doesn't seem to happen on everything though, just certain slides and objects with multiple states.  I cleared down the slide in question completely and then rebuilt the boxes and it did exactly the same again.

I know 5-10 seconds doesn't sound like much but when you are doing multiple changes it becomes unusable.  I have tried it on 2 different PC's, both with reasonably good specs (more than enough to run SL) and it's exactly the same on both, which leads me to think its a SL problem.