MSIEXEC.EXE (installer) problem

For the past week, have had a ton of problems on a normally very stable

computer, seemingly after a Windows Update. Outlook 2003 hangs, IE7 hangs,

BSODs, trouble installing software, error messages with references to audio

drivers not working even though the sound is fine, etc. No locusts or plague

yet, though.

A few error messages have referenced MISEXEC.EXE, e.g., after an attent to

run 'Detect & Repair' in Office 2003. Also get "cannot read/write to memory

address 0x...' messages on startup and during use of IE7. My OS is XP Pro,

Version 5.1.2600 SP2 Build 2600.

I have searched the Knowledge Base and seen some older issues with

MSIEXEC.EXE, but nothing recent. Any thoughts? TIA.