Now it happened again after just a few minutes of use, and WITHOUT sleep/resume. This is CRITICAL. My computer becomes completely unusable, and now it does after only a few minutes of use. This is a disaster. Also, this time instead of rebooting I shut down, and I discovered a funny thing: The splash screen where it freezes it's actually not the first one during boot, but the one that shows up while shutting down. In a rare case of stupid design, they are identical (even Ubuntu was smart enough to differentiate them by having a progress bar move backwards when shutting down).