This is a new configurable feature that is available in v4.0.4 and above.
As an admin, you can decide if you would like to lockdown the client area, or not, if a client has any open abuse reports.
The options are:
The client area is no locked down, and the customers can access other pages freely even if they have open abuse reports
The client area will be locked down only if there are any open abuse reports that the customer has not replied to. Once the customer replies to their open abuse reports, they can freely access other pages in WHMCS
The client area will be locked down if there are any open abuse reports. Only when ALL abuse reports are closed/resolved, they can freely access other pages in WHMCS