Suddenly we can't connect to our Mac. It worked fine before, but all of a sudden it's stopped. restarted the computer checked the connections, but nothing. it's just stuck.

As a Mac user I don't bother with the camera software nor do I download using the camera. Best way to work around the software and firmware incompatibilities is to purchase a memory card reader. The Mac looks at this as an external drive and you can open the memory card see the thumbnails copy and paste the files into a folder in "Documents". Don't know what OS you have but there is a viewer that you can open to see the pictures and if you were successful in loading the camera software you can use it to do your photo editing. My suggestion would be to invest in a Photoshop program. The reason I'm suggesting this is Photoshop is the "industry" standard and by having a multiple port card reader you can change cameras, even memory card types without the hassle of programming compatibilities. Now as far as this "all of a sudden it stopped" what has happened is there was an auto update which basically made the camera download non compatible.
I don't know how old your Panasonic is but there is a lot of people still using "older" digital cameras that work just fine but the computer updates and software is leaving them in the dark. The Mac will work great with the card reader (I'm using Photoshop CS3) and a Photoshop program even if you update the OS. People that are using PC and upgrade to Windows 7 are just dead in the water when it come to the camera software. Oh and another thing that's happening is memory card capacity at one time a 2gig was huge and the camera firmware was compatible with 2gig memory but, if you try putting a larger memory card in say a 4gig the camera won't accept it. I was fortunate with a couple of my Pro cameras where I was able to go onto the manufactures web site and update my cameras. Cheers have a great day ;-)