Modem Connection Loss (important!)?

Hello. I’ve been using ZoneAlarm Firewall for over 6 years and Avira AntiVir for about a year and only now I may be having a serious problem with them.
Whenever I try to upload files to ANYTHING, such as YouTube or MediaFire or any website or anything that involves an upstream, eventually the connection on my modem will suddenly cut out and have to re-connect. Also, I’ve noticed when trying to play games on WiFi, after a while I’ll suddenly get an error message that I’ve been disconnected from the network.
Both of these things have only started happening about a month ago, and it’s getting to be quite frustrating. I’m not 100% sure that the firewall or antivirus is the problem, but most of the time when I shut them both off/disable them, my uploads go just fine, but sometimes the modem disconnections persist.
Is there anything I can do about this? Any help is very much appreciated. Thank you!