The built-in Crossover virus scanner (clamav) will sometimes get stuck when launching Windows applications. To disable Crossover's antivirus scanner go to your Applications folder, right click on CrossOver, and select 'Show Package Details'. Then drill down to /Contents/SharedSupport/CrossOver/etc.
Open 'CrossOver.conf' with a text editor and find the line that reads
;;"AntiVirusScan" = ""
change it to
"AntiVirusScan" = "never"
and save the CrossOver.conf file.