SpywareBlaster database will not update

I have SpywareBlaster (SB) on 3 computers in the house. My wife's computer is a very old Compaq Presario, probably circa 2003(?) and runs XP. I put SB on it when she got it almost 2 years ago and it's worked fine until now. Now when you try to update the database, it seems to download most of it, but then stops and issues an error message (U003) to the effect that the database file is corrupted or the firewall may be blocking the download, and to try again. I have tried

• disabling the Windows firewall, and
• suspending AVG for 10 minutes
• uninstalling SB using RevoUninstaller
• reinstalling SB from both Major Geeks and a second time directly from Brightfort

I have also run a scan with Malwarebytes to see if perhaps some spyware was blocking updates; MB found nothing.

What's wrong?