Antivirus App in ReadyNAS

Hello everybody, my name is Lawrence an i have a problem with antivirus include on my readynas 104 (firmware 6.4.2), i want to say i have a small network 4 computers (W7 32bits) and DLNA TV Samsung. I create on each computers the same sharing (4 sharing folders of the nas), to make it simple, i use only one computer at the same time (the others are off), the internal antivirus is enabled. i can see in my windows explorer my 4 sharing folders (\\192.168.0.50\pictures ... \\192.168.0.50\video ... \\192.168.0.50\music  ... \\192.168.0.50\documents) ... if i try to access one of these sharing (documents for example), it takes too many time to open it and finally i have an error saying me "it's impossible to open the shared folder" (and access the files !) ... i can do it to each sharing, it's same thing !!!

if i disable the internal antivirus, there is no problem, the access to a file in a sharing folder is very quick and i have no problem with the 4 sharing folders. Best of all, i can switch on the 4 computers and the DLNA TV and access at the same time to different files !

What's wrong with the internal antivirus ?     Is there a solution for this ?  

i can't imagine to use a readynas NETGEAR without any antivirus, the NAS is to protect data and not to submit to virus !!!

Waiting for you help

Best Regard  ... Lawrence from FRANCE