Hello Sari,
Sorry to hear that McAffee is blocking your site for a few visitors. The problem is that if it is being blocked, then it should be blocking your site for all visitors. Do you have any specific error messages? It's possible that you have been hacked or have malware on your website. You can request that your site be scanned by submitting a verified support ticket. Also, please review the Recovering from a hack tutorial for further information.
I hope this helps to answer your question, please let us know if you require any further assistance.
Regards,
Arnel C.