I have a doozie here. Amazon.co.uk, news.google.ie, personal.aib.ie/personallogin, and probably more that I haven't found yet, are messed up when I visit them on my laptop, when connected to my home router (wired or wireless). It's the same in all browsers (Edge, FF, Chrome). If I browse to them on my phone (connected to my home WiFi), they are fine. If I connect my laptop to another WiFi, they are all fine. If I view the source of the messed up pages, the HTML is sometimes chopped in the middle, or for example on personal.aib.ie/personallogin, the page looks completely weird and the HTML has been really screwed up. It actually looks like it has been tampered with. If it was malware on my laptop causing this, then surely it would mess it up for all connections? Wired to my WiFi router makes no difference, still messed up. I've scanned the laptop using Avira and Malwarebytes, both reported it to be completely clean. I've updated the WiFi and Ethernet drivers, no difference. The router firmware is up to date. I always use a limited Windows account, no admin (unless updating drivers, etc). I've tried disabling the antivirus, no difference.
I recently updated to Win10, I don't think I had this problem before then (Win 8.1), but I couldn't swear to it. I definitely didn't always have it, I know that Amazon used to load fine. I just don't know when it started. I can't narrow down the problem as it only happens on one laptop, when connected to one router.
Does anyone have any ideas? This has me stumped.