According to the April 18, 2008, notice from USCIS regarding F-1s who received an H-1B visa number but who did not designate change of status because of the cap-gap:
“USCIS has determined that it will allow petitioners of F-1 students whose H-1B petitions were randomly selected to receive an H-1B visa number for FY2009 following the closure of the filing period, to now request a change of status on behalf of qualified beneficiaries, if such requests are received within 30 days of the issuance of the receipt notice.”