ACDSee Photo Editor 4 and ACDsee Photo Editor 2008 will install and update "IDE_ACDstd.apl", and in some cases, this will make your previous version of ACDSee3, ACDSee 4 and ACDSee 5 to disable its own plugins.
To re-enable that IDE_ACDStd plug-in, you can try the following:
In ACDSee, click Tools | Plug-in Settings.
Select the Image Decode tab.
Verify and make sure IDE_ACDStd.apl check box is selected.
ACDSee recommends to update your ACDsee products to the latest version to take advantage of the performance improvement and compatibility with the modern OS and software.