A piece of antivirus software caused computers to stop working after it labelled itself as malware following an update.
The problem developed after components in two programs by Panda Security became corrupted in the patch, an issue the firm said could be worsened if users restarted their machines.
After releasing a recovery tool online, Panda said: "The signature file was repaired immediately. Additionally, a solution for all affected products has been automatically deployed.
"However, in certain environments it is possible for the incident to persist."
Writing on the company website, Panda also provided a list of instructions to help people address the problem, some of which involved booting it in safe mode and running the recovery tool.
Despite reports online that people had lost access to multiple computers, the company said there was no evidence anybody had permanently lost data because of the flaw.
However Alan Woodward, a computer professor at the University of Surrey, told the BBC that data loss was a risk if machines were rebooted.
