In class there are at least 30 out of 40 people using Firefox on Ubuntu with no such issues. On my laptop I use Firefox on Debian with no such issues. Also previously on Windows XP, 7 or 8, both in virtual machines and on hardware, I never had such issues, but that's a while ago so not really applicable anymore.

You might want to submit a bug with your specific hardware to see if anyone can identify the cause, because that's not normal.