Thank you, Carolyn! And thanks for your reply as well!
When I google, the forth and fifth hit is a Swann website with the device:
http://www.google.com.au/search?q=Swann+SW-112-IRA
(Might be because I google via google.com.au.)
Also you can google "Swann" and find their website with the product:
http://www.swannsecurity.com/s/products/view/?product=447
On all these website, you will be able to see the little MacOS compatible Sticker.
As the Software and USB device work fine on windows (and I tested that with my dive computer, otherwise it could have been that the dive computer is broken), I assume that there is a driver issue.
(The device does not mount on MacOS.)
If you google around/look on scuba websites, you'll find plenty of people having similar problems with their dive computers, palsm, mobile phones and Polar devices and it seems to be a mac-specific problem.
The only solution that I could find so far, was to use old macs that came with in built Ir ports, for me not an acceptable solution.
Belkin produces usually Mac-friendly products, but there is no information on their IR USb thing available yet and apple support couldn't help me either.
(
http://www.belkin.com/IWCatProductPage.process?Product_Id=183997)