Capture One 6.3.1 was released today to fix a few crashes/problems in OSX 10.5.8.

It’s good to see Phase One continue to support this older version of OSX but Capture Integration is, in general, strongly recommend 10.5 users upgrade to 10.6 or 10.7 as support for 10.5 from all software vendors will drop off quickly now that 10.7 has been released.

In case you find the cat names easier to remember:
10.5 = Leopard
10.6 = Snow Leopard
10.7 = Lion

http://www.phaseone.com/en/Downloads/CaptureOne.aspx