I too am getting this random freeze every few seconds, and am glad I'm not the only one.
I ran SpeedTest.net, and it returns:
I've rebooted my router and my modem, and my PS3 is the only thing on the network. It is wireless on my router, because I can't do a cable based on locations/walls. I've been playing the game in MP for the past couple of weeks, but it only started freezing up in MP this past weekend (July 20th/21st)
Use wired or HomePlugs (google it). WiFi is unstable sometimes.