Crossover installer seems to dislike v11 of Sage Line 50, but can be installed manually using guidelines:
http://www.codeweavers.com/support/docs/unsupported/
.....and follow information for unsupported applications.
$/opt/cxoffice/bin/wine InsrMsi.exe
$/opt/cxoffice/bin/wine MDAC_TYP.EXE
$/opt/cxoffice/bin/wine ie6setup.exe
Then to install Sage Line 50 v11
$cd Line50/Disk1/
$/opt/cxoffice/bin/wine Setup.exe
...and then continue as normal. I guess that I need to test a little further, but seems ok so far:)
Information provided courtesy of http://www.anothermouse.com