Do you have the Ping Timeout and Ping Count settings the same for both scanning and IP Discovery? These are separate settings. The Scan timeouts can be changed under Preferences and IP Discovery settings under the Discover panel.
Both are set to a default of 1 second (1000 ms) and 3 Ping Counts (or attempts).
IP Discovery works in reverse of Scanning in that it pings a range of IPs, then detects the computer\'s name. Scanning, by default, uses the computer name since IP addresses often change, but computer names rarely do.
Can you ping the problem laptop by its computer name in a DOS Command Prompt? Not just by IP address.