Thanks TeeggerToo! I've just built a new box running Vista Ultimate x64. Video card is Radeon HD4850. Yesterday I installed Impulse and rather rashly installed pretty much all of my OD Ultimate apps. The last thing installed was IconPackager 4.10.172. I applied several MyColors themes, then ran WindowBlinds. I can't be sure exactly when it happened, but the icons (desktop, Quick Launch, Start menu - everywhere) for all my 32-bit apps reverted to the default Windows icon.
I tried different themes and then opened IconPackager for the first time, tried the "repair" buttons and changed icon packages. Through all this, the "Spring" theme's shortcut-overlay remained on every desktop icon. Deleting IconCache.db and the Explorer thumbnails followed by a reboot didn't help. My Aero Glass effects stopped working at some stage. Then I uninstalled WB 6, reset MyColors to the Vista default theme and did a reboot. Aero Glass then worked, and the shortcut-overlays for all desktop icons reverted to a large ugly Vista default. The 32-bit-application icons remained as the (blnk) default.
It was possible to repair some of the 32-bit app icons by changing them to something else (anything but the icon that used to be displayed). Once that change was applied and the icon appeared on the desktop (it didn't always change from the default), I went back into the icon properties and set the icon to the correct one. I soon got tired of doing that.
Finding this thread, I uninstalled IconPackager and ALL the application icons immediately self-repaired. The icons on the desktop still have the ugly large shortcut overlays, so I'm trying to figure out how to repair that - but this is a minor issue. You only realise how important the icons are when you loose them
I raised a ticket with Stardock on this issue.