User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Chrome/10.0.648.204 Safari/534.16 Build Identifier: Firefox 4.0 After my computer rebooted due to a power failure, Firefox is unable to start up normally, it hangs instead eating CPU. Sometimes an empty window is opened (Not Responding), sometimes only the process is seen in Task Manager, eating 5-10% CPU. The other task that is seen eating CPU together with Firefox is lsass.exe (Local Security Authority Process). If I kill the Firefox process, lsass.exe goes back to 0% CPU. Reproducible: Sometimes Steps to Reproduce: 1. Start Firefox 4, open many windows and tabs 2. Hard reset and reboot your PC without quitting Firefox 3. Try to start Firefox 4 again Actual Results: Firefox startup hangs. Expected Results: Firefox should have started up restoring my windows and tabs. I have several extensions installed: XMarks, Image Zoom, Better GMail 2 and a couple others.

Firefox is able to start up again if I clean the cache folders manually.

So the problem is solved and the bug may be closed?

No. My Firefox can start up now, but the bug is still there, and will appear for others. If Firefox is not cleanly quit, it does something with the cache that hangs it for an indefinite time if the cache is large. Bug appeared several times already on both of my computers.

I have browsed the almost 10 years old, but still open, bug 105843. According to that bug will the cache still get lost if Firefox crashes, since the cache is in an unknown state. But the current bug indicates something else.

I see this on Trunk too. Maybe Bug 105843 got exposed more since Disk Cache Size is now dependent on RAM and therefor bigger in most Cases?

This started happening to me when I started using Aurora. I switched to Nightly, and am still seeing it. In my experience, it's not an indefinite hang. But for me, it takes somewhere between 10 and 30 minutes for it to work its way through the entire cache folder. I'm not sure what it's doing, maybe verifying the cache?

Is the Issue less invasive when you limit the Disk Cache Size in Options/Advanced/Network Tab?