According to the iMovie Supported Cameras list, iMovie should support this camera in MPEG2 and AVCHD.
I would suggest the following.
First, make a Camera Archive of your SD Card. You can do this from the import screen. This will give you an exact replica of the contents of your card. You will see why in a minute.
Now, Import all the AVCHD clips from the Card. When finished, delete the AVCHD clips from the Card.
iMovie should now see the MPEG2 clips. You may have to eject the card and reinsert for iMovie to see.
The reason I had you make an Archive is because if you deleted the AVCHD clips and it still did not work, you will still have a copy of them.
If that still does not work, let me know.