If you receive the message 'Undocumented Serious Error (0x101a)' during an update of the virus signature database, it is likely due to one or more damaged update files on your computer. To address the error, please follow the steps below:

1. Open the main program window by clicking the ESET icon next to the system clock or by clicking Start → All Programs → ESET→ ESET Smart Security or ESET NOD32 Antivirus.
    
2. Press F5 to open the Advanced Setup window.
    
3. From the Advanced Setup tree, click Update.
    
4. Make sure that your Update server is set to Choose automatically and your Username and Password are entered correctly.
   
   

   

   
   Important! Make sure your username and password are entered exactly as they are written in your ESET registration email. The username is in the format EAV-12345678 and the hyphen is required. Both the username and password are case sensitive. The password should be ten characters long and all lowercase. If you are copying and pasting, make sure a blank character is not being included in the string. Also, we do not use the letter L in passwords (use the number one (1) instead), a big 0 is the number zero (0), a little o is the letter o.
    

   
   
   Fig. 1-1
   
   

5. Clear the update cache by clicking Clear... and then click OK.
    
6. Restart your computer.
    
7. After restart, open the main program window by clicking the ESET icon next to the system clock or by clicking Start → All Programs → ESET→ ESET Smart Security or ESET NOD32 Antivirus. In the main program window, click Update → Update virus signature database.
    

Your ESET security product should update automatically from now on. If the issue is not resolved, re-installing your ESET security product will be necessary. To uninstall then re-install your ESET security product, please follow the steps below:

NOTE: If using ESET Smart Security 3.0 or ESET NOD32 Antivirus 3.0, we recommend installing version 4.0 for better protection against this issue recurring.

1. Uninstall your ESET software by clicking Start → All Programs → ESET → Uninstall. Restart your computer if prompted.
    
2. Delete the C:\Program Files\ESET folder. Do not delete the Program Files folder, only delete the ESET folder.
    
3. Attempt to re-install your ESET software. If the existence of a third party antivirus product is detected, a warning message with the name of the conflicting antivirus product will be displayed during installation. If this is the case, cancel the install and proceed to step 4. If you are not notified of any conflicting antivirus software on your computer, complete the installation and skip the remaining steps below—you are finished.
    
4. Click here for a list of uninstallers for common antivirus software products (Norton, McAfee, etc.) and click on the appropriate link. After the conflicting antivirus product has been uninstalled, restart your computer and proceed to step 5.
    
5. Re-install your ESET software and restart your computer.