Would you believe this:
1. A web site works with IE8 in VM, I logout from the site. I take a snapshot of the VM
2. I update IE8 in VM to IE11
3. Now I try to login to the site with IE11. It fails, no error, just back to the login screen. (Saw this coming, as it has failed on all other computers and VM's I have except that one). The company is really horrid in this case - their support options only work once you're logged in through the web site and if you have login issues, well - that's apparently impossible. They have phone support but even it doesn't have option for selecting this sort of issue or "bug report".
4. So I rollback to the VM snapshot with IE8. Guess what. Now miraculously, the same login issue exists there!
This company has a java app through which I can login, but all the support buttons redirect to the web site and fail to work when this scenario occurs.
Deleting cookies and changing IP didn't restore the functionality. Clearly they have a server-side check for if someone attempted to log in with IE newer than IE8, well screw them, for good.
Lessons learned: Take also a snapshot *before* logging out. :)
Well I have no clue what is going on. I tried to login dozens of times to the site, and once now and then it does log in. I initially thought it would have something to do with browsers other than IE8, but I now managed to log in 2 times successfully with IE11 out of 20+ attempts. Also support said no such reports have been made. I'm inclined to think the issue is in the server or the router I recently replaced (perhaps it was so cheap because it's spying the traffic?)