OK tried all the wireless settings available to camera and 2 different brands of router. Updated firmware to the latest as well. Have 3 cams and they all behave the same way, it is stable 24x7 on wired, but often (less than a day) needs reboot on wireless, no image and can't connect. This has been the case since day 1, looks like some software issue on this model, or I'm just unlucky with 3 of some faulty batch. Marix simply says it is old model so best I buy new ones.
I'm trying Aztech HD cams next, seems to do HD via wireless stable. Enough of troubleshooting vstarcams for me, it shouldn't be so difficult.