Use the InterNIC Whois Search
tool and view the status of the domain.
Look for a line that says:
Following is an example whois record of a suspended domain:
The "clientHold" status indicates that the domain has been suspended because validation process was not completed within 15 days after the first validation request was sent to the owner email address on the domain's whois record. Either the owner of the domain ignored requests to verify their contact information, or the requests are in their spam folder, or the email address listed on the domain for the domain owner is invalid.
To recover a domain in this status, see:
Recovering a Suspended Domain