I own a HP wireless keyboard mouse which use the same USB dongle to connect to the PC. The keyboard works in BIOS and GRUB but when I reach the login screen, they stop working. It worked earlier after rebooting a few times but then they stopped doing that either. There are some messages displayed before it switches to login screen (something about USB device not accepting address- am trying to get the exact message but it goes away too fast), I could add that in as well as any outputs you require (like lsusb or lspci).
I found the problem and fixed it- apparently my BIOS was using USB 2.0 protocols to access USB drives but after Ubuntu took over they were using USB 3.0 protocols, which made a mess. Came upon the solution by fluke actually- was just looking in my BIOS setup and there it was. It's useful when using external DVD reader to install OS, but becomes a hassle afterwards, as it did for me.