failing that, take a look at the processes in Activity Monitor (Applications > Utilities > Activity Monitor and see if there's a process that's hogging CPU.
failing that, boot into safe mode and see if it still happens
failing that, have you tried deleting com.apple.finder.plist from your user account?
failing that, take a look at the processes in Activity Monitor (Applications > Utilities > Activity Monitor and see if there's a process that's hogging CPU.
failing that, boot into safe mode and see if it still happens
failing that, have you tried deleting com.apple.finder.plist from your user account?