The kvm download page mentions that versions 76 onwards need kernel 2.6.25. What it doesn't mention is what happens if you overlook this requirement. Which is that VMs will hang on the BIOS screen, just after the “Press F12 for boot menu” prompt. You don't get any kind of error message anywhere, so searching the web for help doesn't reveal much. In other words, the kind of issue you could easily bang your head against for a couple of hours.