Panda antivirus users were dished up a nasty shock yesterday (or today if you were one of the ones who shut your computer off) when an error in yesterday's update "may have caused some files to be moved to quarantine". This is a rather polite way of saying "your computer is now screwed".
This error must have stopped a lot of hearts when it cropped up. When Panda discovered this, they quickly issued a new signature file to correct the issue. However, that didn't help people who couldn't boot their computer.
Here's the scoop. When the signature file was installed, it mistakenly saw vital pieces of software that Windows relies on to run, as malware and moved them into quarantine. This, in effect, turned computers into bricks - unbootable and unusable when you tried to restart. As long as you didn't reboot, you were fine. The update issued by Panda corrected the problem and most people weren't even aware of the problem. Rebooting or shutting down meant you wouldn't be able to log into your account. The files your computer relies on to let you log into Windows were no longer available and you were stuck.
If you are one of the unlucky ones who rebooted, Panda has issued a couple of fixes to get you back up and running. Go to their webpage ➙ http://www.pandasecurity.com/uk/homeusers/support/card?id=100045 and follow the onscreen instructions. You'll need access to a computer and usb stick to download their ps-recovery.exe file. Once you have it, the instructions are very clear and easy to follow. You'll be up and running again in a short time.