If you start experiencing STOP errors after a recent Windows Update and are running AVG Anti-Rootkit or spyware, KB938371 may be the cause of your troubles. This update, a patch for the Windows Trusted Installer, has reportedly caused error 0x0000007E in avgarkt.sys and 0x000000D1 after uninstallation of Anti-Rootkit if Anti-Spyware is left in place. It can apparently cause a cascading failure through these particular products and possibly AVG's Antivirus as well. It also happens to be a prerequisite to installing Service Pack 1 RC1 for Vista.

The remedy for this situation is booting into safe mode and uninstalling the offfending products (this includes most other security software, such as third party firewalls). Once KB938371 is installed through Update, the Anti-Spyware and Anti-Rootkit can usually be re-installed without further problems (after you install KB943302, release on the same day, fixes some incompatibilities with the Anti-Spyware package) . A similar problem can affect Comodo Personal Firewall.