I’ve had the same problem for a few weeks. Most app on my phone were working just fine, but when downloading or updating apps I got error 495 (I have not tried using wifi). I tried all the solutions posted online but nothing worked, finally out of pure desperation I tried to check all my settings... It turned out my internet settings was wrong - for some reason my access point had been changed from “internet” to “WAP”. When using WAP your device will have internet access and most apps will work, but when downloading or updating you will get error 495. To solve the problem I just required a new internet configuration from my service provider – as soon as I got the new settings my phone started to update all apps.
To check access point go to “settings – more – mobile networks – access point names” (LG P990 - android 4.0.4)
Hope this can help some of you with the dreaded error 495 :D