FYI: I had problems with autodownloading older and newer codecs. I got this solution from support:
You can also try manually loading the codecs from here
http://www.microsoft.com/windows/windowsmedia/format/codecdownload.aspx
Use the codec package from the bottom of the page, in CrossOver setup select the install of Media Player again and just select other *.exe rather than downloading WMP 6.4 again, point the install wizard at the codecs package.